A visual guide to Google search ranking volatility by Dr. Peter J. Meyers. Hotter days represent more movement on page one of the Google search results.
Quality Update
May 3rd, 2015
Penguin 4.0 / R-T
Sept 27, 2016
Unknown Update
May 17, 2017
March 2018 Core
March 8, 2018
August 2018 Core
August 1, 2018
COVID 19 Pandemic
March 11, 2019
May 2022 Core
May 25, 2022
August 2023 Core
August 22, 2023
Early February marked extreme ranking flux, with MozCast hitting its second-highest all time temperature: 140° on February 3. Google announced a major update to Google Discover on February 5, but there was no indication that this impacted regular, organic results.
Google's third announced Core Update of 2025 rolled out on December 11, lasting about 18 days. Ranking flux in MozCast spiked at 122° on December 12. Industry research showed notable gains for e-commerce and news sites and losses for healthcare sites.
Multiple tools and webmaster chatter indicated heavy search ranking flux, which hit 123.0°F on MozCast. No update was officially confirmed by Google.
Google released their first confirmed Spam Update since the end of 2024, lasting nearly a month and peaking in mid-September in our MozCast data (123.4° on September 16). Recent public comments by Liz Reid suggested that Google has broadened their definition of spam.
The second Core Update of 2025 rolled out on June 30 and lasted just under 17 days. MozCast peaked at 124.4° on July 9, but also saw a spike at the very end of the update on July 17. There were some reports of recoveries from earlier Helpful Content Updates.
Google rolled out the first Core Update of 2025 on March 13, which lasted 13 days. MozCast peaked at a historically very high temperature of 130.1° on March 20, but unusually high temperatures were observed throughout most of March.
A week before the March Core Update, MozCast registered ranking flux of 121.7°F. High volatility continued into the official start of the Core Update.
On February 19, MozCast hit 125.8°F, with multiple tracking tools showing spikes in ranking flux. No update was confirmed by Google.
Just a day after the December Core Update ended, a major Spam Update rolled out, lasting 7 days, including the Christmas holiday (ending on December 26). MozCast peaked at 123.9°F on December 19.
Right on the heels of the November Core Update, Google rolled out a short December Core Update, lasting only six days. Early reports indicated high impact. MozCast peaked at 127.0°F at the very end of the update, historically high even by 2024 standards.
The November Core Update rolled out over 24 days. While ranking flux was high on a few days, this update crossed the US Thanksgiving holiday, including Black Friday and Cyber Monday, and the long timespan was difficult to disentangle.
Rank tracking monitors showed massive flux on Election Day in the US, with MozCast hitting 120.7°F. It's unclear whether this was a Google update or caused by the dynamic nature of the news cycle itself and corresponding content shifts.
Google broadened the Site Reputation Abuse manual actions, with high-profile hits on third-party content on major brands. The exact timing is unclear, but confirmed penalties began in late September and may have lasted for a few weeks.
A new Core Update officially kicked off on August 15 and rolled out over 19 days. Unfortunately, the total impact was very difficult to assess, given a multi-day overlap with a serious rankings issue. Most measurable ranking flux occurred early in the update.
The Google Search Status Dashboard reported an "ongoing issue" with rankings that lasted roughly five days. This event overlapped with the August 2024 Core Update. MozCast recorded a temperature of 149.1°, the highest ranking flux we've ever measured.
After rolling out to all signed-in US searchers in May, AI Overviews began to appear in signed-out and incognito searches. The prevalence of AI Overviews for signed-out searches has continued to increase since mid-August but remains volatile.
MozCast and other ranking flux tools detected about two days of high volatility, peaking at 117.4° on July 30. Google did not confirm an update or other event.
In late June, Google announced that they would be dropping continuous scroll on desktop search results and returning to paginated results. This change had no clear impact on rankings but may have impacted click-through rates for deeper results.
Google rolled out a spam update, with general guidance (no specifics), including a likely update to SpamBrain data. The rollout lasted about a week, and MozCast peaked at 117.2° on June 27, at the very tail-end of the update window.
Google rolled out AI Overviews (previously the Search Generative Experience) from Google Labs to all logged-in US searchers. Immediate reactions were mixed, with people seeing more problematic answers than in previous SGE testing.
After pre-announcing in March, Google took action against sites using their reputation to promote low-relevance content, such as coupon directories. Initial results were targeted, wiping out rankings for sections of major brands. Google confirmed that this first round was manual actions and is not algorithmic yet.
Google released another core update, which rolled out over an unprecedented 45 days! The March 2024 Core Update integrated the Helpful Content Updates (HCU) into the core algorithms, and Google claimed that the latest changes will reduce unhelpful content in search results by 40%. MozCast temperatures spiked to 120.0°F on March 8 and topped 110°F on three other days in March.
Concurrently with the March Core Update, Google rolled out a susbtantial new spam update over about 15 days. This update included new policies targeting scaled content abuse and expired domain abuse. Reports from the SEO community suggested that a wave of manual penalties may have followed this update.
MozCast and other ranking volatility trackers measured a massive spike, with MozCast hitting 120.4°F. This was the hottest day of 2024 for MozCast, and the 15th hottest day recorded by our systems over the past decade.
Google reported an indexing bug starting around February 1 and lasting roughly seven days. MozCast peakes at 111.6°F on February 7. Site owners reported indexing issues prior to this, well into January, which Google may not have been aware of until later.
Google confirmed a search ranking bug where sites were disappearing from rankings, but the exact timing was unclear. MozCast peaked at 107.9°F on January 23, a couple of days after the situation was supposed to be resolved.
Rank-tracking tools spiked mid-week, with MozCast peaking at 111.4°F on January 10. Google did not confirm an update.
The November Reviews Update rolled out over almost a fully month, peaking in MozCast at 115.8°F at the very end. Ranking volatility was high throughout November. Google stated that this would be the last announced Reviews Update.
Less than a month after the last Core Update, Google rolled out another Core Update on November 2. MozCast spiked at 115.4°F on November 6. Interestingly, Google confirmed that this update impacted a "different core system," confirming the existence of multiple "core" algorithms.
Launching just a day after the Spam Update, the October 2023 Core Update also rolled out over two weeks. The overlap of the two updates made separating their impact nearly impossible. As usual, Google did not provide specifics about this Core Update.
Google officially rolled out a Spam Update over about two weeks, and peaking at 111.1°F on October 9. Officially, this update improved spam detection in a number of non-English-speaking markets. Unfortunately, it overlapped completely with the October 2023 Core Update.
After a partial drop in August, indented results disappeared from Google SERPs (in MozCast tracking) entirely on September 20. Google confirmed this change a few weeks later. This resulted in less clustering of results from a single domain, with indented results dropping to their original rankings.
The third official Helpful Content Update (and first of 2023) officially rolled out over 13 days, peaking at 110.6°F on September 14. Industry consensus was that this HCU hit harder than the previous two, possibly in the wake of AI-generated content.
Google confirmed the second Core Update of 2023, beginning on August 22 and officially lasting 16 days. Unfortunately, due to massive July and August ranking flux, specific details are unclear. MozCast peaked on August 23-24 at 122.7°F.
August 18 registered massive ranking flux, with MozCast measuring 127.4°F. The prevalence of page-one indented results dropped 50%. Since some indented results are promoted from lower ranking positions, this caused substantial shake-ups in page-one rankings.
Google announced that rich results based on How-To and FAQ structured data would be reduced in some situations. As of September 2023, these changes had only partially materialized, with FAQ results showing no reduction on desktop searches.
MozCast registered a spike of 122°F on July 17, and this was just one of a number of record days across the summer of 2023. Other flux-tracking tools showed similar spikes, even in the absence of confirmed Google updates.
Google officially launched the Search Generative Experience (SGE), adding "AI" results (powered by Google Bard) to the top of some searches. This initial rollout was only to opt-in, signed-in users.
Google rolled out a new Reviews Update, expanding the scope of these updates beyond product reviews and into businesses, services, destinations, and media. This rollout lasted just under two weeks.
Google confirmed a Core Update, beginning on March 15th and officially lasting for 13 days. On the first day of the roll-out, MozCast peaked at 108.7°F, and six days measured above 100°F. As with most Core Updates, Google's guidance was non-specific.
A Product Reviews Update rolled out over two weeks, peaking at a whopping 112.2° on MozCast on February 28 , with four days in that period exceeding 100°F. This PRU also expanded beyond English-language queries, adding 10 languages.
MozCast measured two days of very-high flux (February 15-16), peaking at 106.4°F on Febtuary 16. While there were some reports of ranking shake-ups, Google did not confirm an update.
Google announced an extra 'E' in E-A-T, stressing the importance of first-hand Experience. It's unclear when and how this impacted the algorithm, but it does represent a significant change to Google's Quality Rater Guidelines that will likely drive future algorithm updates.
Google announced a targeted Link Spam Update that rolled out over almost a full month. Documentation specifically mentioned the 'SpamBrain' AI system in this update, but official details were limited. This update substantially overlapped with the December 2022 HCU.
More than a year after bringing continuous scroll search results to mobile, Google announced the desktop launch. While this had limited impact on rankings, the change undoubtedly impacted click-thru rates (CTRs) and other engagement metrics, especially beyond page one.
The December Helpful Content Update (HCU) took over a month to roll out, overlapping with the Link Spam Update. MozCast topped 100°F on five days during this time period, but separating the impact of the two updates is extremely difficult.
After almost a year, Google officially announced an update to their spam detection systems. This update did not specify link spam. The update lasted about 48 hours, peaking at 104.2° on MozCast on October 21st.
Google released their fifth Product Reviews Update, lasting until September 26th. This update completely overlapped the September Core Update. Ranking flux across both updates peaked at 94.7° on September 21st, wrapping up a tumultuous month.
The second Core Update of 2022 rolled out on the heels of the Helpful Content Update, complicating any attempts at analysis. The update officially lasted until September 26th, but ranking flux spiked early, with MozCast measuring 94.0° on September 12th.
The Helpful Content Update aimed to reward "people-first" content and devalue content written primarily for SEO. It officially rolled out over two weeks (wrapping up on September 9th), with an unusual pre-announcement just one week in advance. There were no clear signs of broad impact.
An accident at a Google data center in Council Bluffs, Iowa may have resulted in massive ranking fluctuations, with MozCast hitting a historical high of 123.6°F. In some cases, searchers could not access results at all. Search results appeared to normalize the next day.
Google's fourth Product Reviews Update (PRU) rolled out over the course of a week, wrapping up on August 2nd. Ranking flux on MozCast peaked at 98.8° on the last day of the update. There were no details from Google on how this update differed from the previous three PRUs.
MozCast measured high volatility on both July 8th (103.9°) and July 6th (101.9°). While some SEOs and rank tracking tools observed major changes during this time period, Google did not confirm an update, and no clear details emerged.
MozCast spiked at 109.0° on June 27th, measuring unusually high ranking flux even for a historically high-activity summer. Google provided no details nor confirmation, and the nature of the update remains unclear.
On May 25th, Google announced the rollout of a core update. The rollout lasted roughly 2 weeks and was completed on June 9th. MozCast recorded peak ranking flux at 103.0°F on May 25th, the first day of the rollout. As with most Core Updates, Google did not provide specifics.
Google confirmed a significant product reviews update and changed the naming convention to match the Core Updates. The update officially took 19 days to roll out, starting on March 23rd, and built on previous product review updates to identify high quality product reviews.
Multiple SERP trackers picked up high flux around March 18-19, with MozCast peaking at 101.1°F on March 18th. No update was officially confirmed, and Danny Sullivan of Google tweeted that "I did check, no one knows of any broad, major update."
Google announced that the Page Experience Update previously released on mobile SERPs would be rolled out to desktop. This rollout officially occurred from February 22nd to March 3rd. MozCast peaked at 99.4°F on March 3rd and 98.8°F on February 23rd.
MozCast measured historically high ranking flux of 105.4°F on February 5th, with a possible aftershock of 102.5°F on February 7th. Some other flux trackers picked up similar spikes, but no update was officially confirmed.
During a period of relatively high volatility, MozCast recorded a temperature spike of 102.1°F on January 10th. No Google update was confirmed, but industry chatter picked up ranking changes on January 11th.
MozCast measured very high volatility, peaking at 105.0°F, just two days after recording a temperature of 101.3°F. While Google did not confirm these specific dates, both events occurred during the December 1-21 rollout of the Product Reviews Update.
While not a traditional algorithm update, Google released a major overhaul to the design of Top Stories, splitting it into two columns on desktop and (in many cases) dramatically increasing the amount of SERP real estate occupied by news results.
On December 1, Google announced another update to reward high-quality product reviews (and a refresh of the April 2021 update). This update reportedly rolled out over three weeks, and MozCast recorded multiple days of high SERP volatility in December.
On November 17, Google announced the rollout of a core update. While this update officially wrapped up at the end of November, most tracking sites showed a strong single-day spike (with MozCast hitting 101.7°F on November 17). The overlap with Black Friday sparked controversy in the SEO community.
Google announced another broad spam update, which rolled out over about 8 days. MozCast peaked at 96.9°F on November 2nd. Unlike the July update, Google did not specifically call this a "link spam" update and did not provide much detail about the sites and tactics targeted.
MozCast measured two days of high flux on October 1-2, peaking at 100.9°F on October 2nd. Multiple tools and SEOs observed major ranking changes, but Google did not confirm this update and no explanation has been reported.
Starting around August 16, SEOs began to notice a substantial increase in Google rewriting page titles in SERPs. Google later confirmed this change (but not the exact date), and, after many complaints about result quality issues, scaled back some of the changes in September.
Google announced a link spam update that reportedly rolled out over 2-4 weeks. According to Google, this was a broad algorithm update across multiple languages. MozCast showed heavy flux on July 28, spiking at 100.3°F.
A follow-up to the June Core Update, the July 2021 Core Update rolled out from July 1-12. Peak volatility on MozCast hit 102.7°F on July 1st, but we saw temperatures in the 90s on July 5th, 8th, and 11th. Like most Core Updates, Google was light on specifics.
After multiple delays, Google started rolling out the Page Experience Update on June 25th, announcing that the rollout would continue through August 2021. This update included Core Web Vitals and impacted both organic results and News results (including Top Stories).
Google released two spam updates, on June 23rd and June 28th. It was unclear how the two updates were connected or what specifically was impacted. While specific sites showed significant impacts, there was no clear impact on overall rankings volatility.
In an unprecedented move, Google simultaneously announced the (apparently connected) June and July 2021 Core Updates. The June Core Update reportedly rolled out from June 2-12, peaking in MozCast at a temperature of 107.3°F on June 3rd.
Google announced an update to reward in-depth reviews over thin reviews and spammy affiliates (impacting English-language only at launch). While the update seemed focused on review quality, the exact factors involved appear to be complex.
Three weeks after roughly 40% of Featured Snippets mysteriously disappeared from SERPs, they just-as-mysteriously returned to their previous levels. Google did not provide confirmation nor an explanation.
MozCast registered a 40% day-over-day drop in SERPs with Featured Snippets, their lowest point since 2015. On further inspection, these were heavily focused on short queries (especially 1-word queries) and disproportionately hit YMYL queries (health and finance).
Google rolled out so-called "passage indexing" (which is probably closer to passage ranking) for US/English queries. While we measured two days of moderate rankings flux, it was unclear exactly how the update impacted SERPs. Google initially estimated this update would impact 7% of queries.
One day after Google announced the end of the December Core Update rollout, MozCast measured moderately-high rankings flux at 99°F. It was unclear whether this was the last hurrah of that rollout or a separate, medium-sized algorithm update.
Google announced a Core Update that appeared to roll out quickly, with the bulk of the impact hitting on December 3rd. MozCast hit 112°F, on par with the March 2020 Core Update and August 2018 "Medic" Update. Some sites reported reversals a few days later, but this seems to have been limited.
Google claimed that the bulk of the indexing and canonicalization bug(s) had been fixed by around October 14th. MozCast measured a drop in indexed pages and a temperature of 104°F around October 12th, with temperatures in the 90s lasting for a few days after.
Google confirmed an indexing and canonicalization bug starting in early September. MozCast measured temperatures of 99°F on September 29th and 30th, and detected dips in indexed pages on September 23rd and 29th.
Rank tracking tools and webmaster chatter suggested a significant update, with MozCast measuring 101°F, but no update was confirmed by Google. Some industry analysts suggested the changes were rolled back the next day and may have been temporary.
SEOs reported massive ranking changes for a few hours on August 10, which then seemed to disappear. Google later confirmed a glitch in their indexing systems. MozCast registered 97°F the following day (August 11), but it's unclear if this event was related.
Rank-tracking tools showed heavy flux, with MozCast reaching 96°F. While no algorithm update was confirmed, a Google rep confirmed an indexing bug affecting Disqus comments that would be fixed during this time period.
Google announced another Core Update (the second of 2020), which caused heavy rankings flux from about May 4-6. Peaking at 113°, it measured on MozCast as the second-highest Core Update after the August 2018 "Medic" update.
While not an algorithm update, per se, COVID-19 dramatically shifted consumer search behavior. The WHO pandemic declaration on March 11th seemed to be a pivotal turning point. In March on MozCast, 16 out of 31 days topped 90°F, and rankings were in high flux well into April and May.
Multiple tools registered very high ranking flux for a few days (MozCast peaked at 116° on February 7th). Google reps said that this was not a Core Update, and some data sets showed these changes reversing around February 12th.
Google announced that URLs in Featured Snippets would no longer be appearing as traditional organic results, in line with Google's philosophy that a Featured Snippet is a promoted organic result. This had significant implications for rank-tracking and organic CTR.
Google rolled another core update, with MozCast showing heavy flux across three days and a high temperature of 97°F, in line with the previous three core updates (but smaller than the August 2018 "Medic" core update).
Google confirmed that the BERT natural language processing algorithm was rolling out internationally, in 70 languages. This announcement came after speculation from the SEO community, and the exact timing of the roll-out is unclear.
Google upgraded their algorithm and underlying hardware to support the BERT natural language processing (NLP) model. BERT helps Google better interpret natural language searches and understand context.
SERP trackers registered multiple days of ranking flux, with MozCast showing early signs on October 2 and peaking at 98°F on October 4. Google did not confirm an update, and no details were forthcoming.
Google rolled out another core update. The update measured at 97°F on MozCast (fairly high, but not historically high) and seemed to impact sites affected by previous core updates. Google did not provide many details.
Ranking trackers and webmaster chatter registered a week of heavy flux (MozCast peaked at 95°F on July 16) that was later dubbed the "Maverick" update by the search community. Google did not confirm an update, and details were limited.
Google pre-announced a "site diversity" update, claiming it would improve situations where sites had more than two organic listings. Moz data showed that, while the update did marginally improve SERPs with 3-5 duplicate sites on page one, the impact was relatively small.
Google pre-announced a "core" update, but with limited details. Sites impacted in previous core updates seem to have been affected, in some cases, and some major UK publishers reported heavy losses. On average, the impact was smaller than the August "Medic" update, as measured by MozCast.
Two days in a row, Google confirmed indexing bugs. The first bug reportedly was preventing new content from being properly indexed. MozCast confirmed unusually high SERP flux from May 23-25 (peaking on the 23rd), but it's unclear if this was directly related to the bugs.
Google confirmed a bug that dropped pages from the search index around the weekend of April 5th. Moz data suggested drops on April 5th and 7th, with about 4% of stable URLs falling off of page one. Most sites recovered soon after.
Google confirmed a "core" update, stating it was the third major core update since they began using that label. MozCast hit a peak of 101.2°F, a bit below March 1st temperatures. No specific details were given about the nature of the update.
For one day, Google showed anomalous page-1 counts, with up to 19 organic results. These appeared to be related to In-depth Articles, which disappeared entirely on March 6. MozCast reached 108.2°F, but it's unclear how much of this was due to the temporary boost in organic counts.
After a relatively quiet December and January, tracking tools detected heavy ranking flux, with MozCast reaching 103.4°F.
MozCast hit 103.1°F, and webmaster chatter and other tracking tools indicated high algorithm flux. Google did not confirm.
Tracking tools and webmaster chatter indicated heavy algorithm flux, and MozCast spiked to 109.7°F. No confirmation from Google.
MozCast temperatures hit 107.6°F, and webmaster chatter around an update spiked, but Google would not confirm any significant changes.
Google confirmed a "broad core algorithm update," with wide reports of massive impact. It rolled out over the period of about a week, but peaked on August 1-2. This update seemed to disproportionately affect sites in the health and wellness vertical, although large-scale impact was seen in all verticals.
After warning users of unsecured (non-HTTPS) forms months earlier, Chrome 68 began marking all non-HTTPS sites as "not secure." The changes rolled out on July 24, but rely on users installing the latest Chrome version, which can take weeks or months.
Algorithm trackers and webmaster chatter signaled heavy rankings flux, but Google did not confirm. MozCast recorded its highest temperature in 2018 at 114°F.
Six months after announcing it, Google rolled out the mobile page speed update, making page speed a ranking factor for mobile results. Google claimed that this only affected the slowest mobile sites, and there was no evidence of major mobile rankings shifts.
Google moved videos from organic-like results with thumbnails into a dedicated video carousel, causing a shake-up in results that were previously tracked as organic. At the same time, the number of SERPs with videos increased significantly (+60% in MozCast).
Algorithm tracking tools and webmaster chatter showed heavy activity, but Google did not confirm an update. MozCast showed very high temperatures over a 3-day period, peaking on May 23.
After testing longer display snippets of up to 300+ characters for a few months, Google rolled back most snippets to the former limit (about 150-160 characters).
MozCast picked up heavy algorithm flux that peaked on April 17 and continued for over a week. Google later confirmed a "core" update, but didn't provide any specifics and the update wasn't named by Google or the SEO community.
Google announced that the mobile-first index was finally "rolling out." Since the index has been in testing for many months, and Google has suggested they are migrating sites gradually, it's unclear how much impact this specific roll-out had on the overall index. Webmaster should begin to see notifications within Google Search Console.
On a small set of Knowledge Cards, including some time/date queries and unit conversion calculators, Google started displaying zero organic results and a "Show all results" button. A week later, Google stopped this test, but we believe it is an important sign of things to come.
Google confirmed a "core" update on March 7th, but volatility spiked as early as March 4th, with a second spike on March 8th, and continued for almost two weeks. This may have been multiple updates or one prolonged, rolling update. The "Brackets" name was coined by Glenn Gabe; no details were provided by Google.
Rankings showed a spike in volatility (across a number of tools) around February 20th, which quickly settled down, sometimes signalling a targeted algorithm update. Google did not confirm any update in this time period.
Chatter and several tools showed ranking volatility around December 14th. Barry Schwartz named this the "Maccabees" update, but Google would only confirm that several small updates had happened in the general timeline. Pre-holiday updates tend to get more attention (and are generally rarer) due to their disruptive effect on e-commerce.
After testing longer search snippets for over two years, Google increased them across a large number of results. This led us to adopt a new Meta Description limit -- up to 300 characters from the previous 155 (almost doubling). Google confirmed an update to how snippets are handled, but didn't provide details.
Algorithm trackers and webmaster chatter detected a high amount of flux, peaking (in our data) around November 15. Google did not confirm an official update.
Over a period of a few days from October 27-31, there was a substantial drop in Featured Snippets. This co-occurred with a jump in Knowledge Panels, as Google seemed to add many panels for broad terms and objects ("travel", "toilet", "web design", etc.). Some of these panels disappeared around December 15.
With the launch of Chrome 62, Google started warning visitors to sites with unsecured forms. While not an algorithm update, this was an important step in Google's push toward HTTPS and may have a material impact on site traffic.
Algorithm trackers (including MozCast) and webmaster chatter spotted increasing flux starting around September 25th, which seemed to spike on the 27th, after a period of relative calm. No update was officially confirmed.
Google officially launched their jobs portal, including a stand-alone 3-pack of job listings in search results. These results drew data from almost all of the major providers, including LinkedIn, Monster, Glassdoor, and CareerBuilder.
MozCast and other tools tracked a massive, multi-day spike that kicked off around May 17th. This preceded a sustained period of high algorithmic flux that may not have settled down for months.
According to our MozCast 10K tracking set, half of page-1 Google organic results were secure/HTTPs as of mid-April. This increased to close to 75% by the end of 2017.
Google rolled out what appeared to be a major update, with reports of widespread impacts across the SEO community. Gary Illyes jokingly referred to is as "Fred", and the name stuck, but he later made it clear that this was not an official confirmation.
Algorithm changes beginning on February 1st continued for a full week, peaking around February 6th (some reported the 7th). Webmaster chatter and industry case studies suggest these were separate events.
There was a period of heavy algorithm flux starting around February 1st and peaking around February 6th. It is unclear whether this was multiple algorithm updates or a single update with an extended roll-out, but anecdotal evidence suggests at least two updates.
Google started rolling out a penalty to punish aggressive interstitials and pop-ups that might damage the mobile user experience. Google also provided a rare warning of this update five months in advance. MozCast showed high temperatures from January 10-11, but many SEOs reported minimal impact on sites that should have been affected.
Multiple Google trackers showed massive flux around December 14-15, including a rare MozCast temperature of 109°F. Webmaster chatter was heavy as well, but Google did not confirm an update.
MozCast detected a major (106°) spike on November 10th and another on the 18th. Industry chatter was high during both periods, with some suggesting that the second spike was a reversal of the first update. Google has not confirmed either event. Many people reported bad dates in SERPs during the same time period, but it's unclear whether this was causal or just a coincidence.
The second phase of Penguin 4.0 was the reversal of all previous Penguin penalties. This seemed to happen after the new code rolled out, and may have taken as long as two weeks. Post-Penguin activity had one final peak on October 6th (116°), but it is unclear whether this was Penguin or a new update. Algorithm temperatures finally started to drop after October 6th.
The first phase of Penguin 4.0, which probably launched around September 22-23, was the rollout of the new, "gentler" Penguin algorithm, which devalues bad links instead of penalizing sites. The exact timeline is unconfirmed, but we believe this rollout took at least a few days to fully update, and may have corresponded to an algorithm temperature spike (113°) on September 27th.
After almost two years of waiting, Google finally announced a major Penguin update. They suggested the new Penguin is now real-time and baked into the "core" algorithm. Initial impact assessments were small, but it was later revealed that the Penguin 4.0 rollout was unusually long and multi-phase (see September 27th and October 6th).
MozCast recorded a nearly-record 111° temperature and a 50% drop in SERPs with image (universal/vertical) results. The universal result shake-up opened up an organic position on page 1, causing substantial ranking shifts, but it's likely that this was part of a much larger update.
While unconfirmed by Google, MozCast recorded extreme temperatures of 108° and a drop in local pack prevalence, and the local SEO community noted a major shake-up in pack results. Data suggests this update (or a simultaneous update) also heavily impacted organic results.
Just more than a year after the original "mobile friendly" update, Google rolled out another ranking signal boost to benefit mobile-friendly sites on mobile search. Since the majority of sites we track are already mobile-friendly, it's likely the impact of the latest update was small.
MozCast and other Google weather trackers showed a historically rare week-long pattern of algorithm activity, including a 97-degree spike. Google would not confirm this update, and no explanation is currently available.
Google made major changes to AdWords, removing right-column ads entirely and rolling out 4-ad top blocks on many commercial searches. While this was a paid search update, it had significant implications for CTR for both paid and organic results, especially on competitive keywords.
Multiple tracking tools (including MozCast) reported historically-large rankings movement, which Google later confirmed as a "core algo update". Google officially said that this was not a Penguin update, but details remain sketchy.
Google made a major announcement, revealing that machine learning had been a part of the algorithm for months, contributing to the 3rd most influential ranking factor. *Note: This is an announcement date - we believe the actual launch was closer to spring 2015.
Google announced a Panda update (most likely a data refresh), saying that it could take months to fully roll out. The immediate impact was unclear, and there were no clear signs of a major algorithm update.
After many reports of large-scale ranking changes, originally dubbed "Phantom 2", Google acknowledged a core algorithm change impacting "quality signals". This update seems to have had a broad impact, but Google didn't reveal any specifics about the nature of the signals involved.
In a rare move, Google pre-announced an algorithm update, telling us that mobile rankings would differ for mobile-friendly sites starting on April 21st. The impact of this update was, in the short-term, much smaller than expected, and our data showed that algorithm flux peaked on April 22nd.
Multiple SERP-trackers and many webmasters reported major flux in Google SERPs. Speculation ranged from an e-commerce focused update to a mobile usability update. Google did not officially confirm an update.
Significant Google Search Algorithm Update Yesterday (SER)
Google Brand-eCommerce “Update” causing fluctuations (Searchmetrics)
Google's major local algorithm update, dubbed "Pigeon", expanded to the United Kingdom, Canada, and Australia. The original update hit the United States in July 2014. The update was confirmed on the 22nd but may have rolled out as early as the 19th.
A Google representative said that Penguin had shifted to continuous updates, moving away from infrequent, major updates. While the exact timeline was unclear, this claim seemed to fit ongoing flux after Penguin 3.0 (including unconfirmed claims of a Penguin 3.1).
More than two years after the original DMCA/"Pirate" update, Google launched another update to combat software and digital media piracy. This update was highly targeted, causing dramatic drops in ranking to a relatively small group of sites.
More than a year after the previous Penguin update (2.1), Google launched a Penguin refresh. This update appeared to be smaller than expected (<1% of US/English queries affected) and was probably data-only (not a new Penguin algorithm). The timing of the update was unclear, especially internationally, and Google claimed it was spread out over "weeks".
Google made what looked like a display change to News-box results, but later announced that they had expanded news links to a much larger set of potential sites. The presence of news results in SERPs also spiked, and major news sites reported substantial traffic changes.
Google announced a significant Panda update, which included an algorithmic component. They estimated the impact at 3-5% of queries affected. Given the "slow rollout," the exact timing was unclear.
Following up on the June 28th drop of authorship photos, Google announced that they would be completely removing authorship markup (and would no longer process it). By the next morning, authorship bylines had disappeared from all SERPs.
After months of speculation, Google announced that they would be giving preference to secure sites, and that adding encryption would provide a "lightweight" rankings boost. They stressed that this boost would start out small, but implied it might increase if the changed proved to be positive.
Google shook the local SEO world with an update that dramatically altered some local results and modified how they handle and interpret location cues. Google claimed that Pigeon created closer ties between the local algorithm and core algorithm(s).
John Mueller made a surprise announcement (on June 25th) that Google would be dropping all authorship photos from SERPs (after heavily promoting authorship as a connection to Google+). The drop was complete around June 28th.
Less than a month after the Payday Loan 2.0 anti-spam update, Google launched another major iteration. Official statements suggested that 2.0 targeted specific sites, while 3.0 targeted spammy queries.
Google confirmed a major Panda update that likely included both an algorithm update and a data refresh. Officially, about 7.5% of English-language queries were affected. While Matt Cutts said it began rolling out on 5/20, our data strongly suggests it started earlier.
Just prior to Panda 4.0, Google updated it's "payday loan" algorithm, which targets especially spammy queries. The exact date of the roll-out was unclear (Google said "this past weekend" on 5/20), and the back-to-back updates made the details difficult to sort out.
Major algorithm flux trackers and webmaster chatter spiked around 3/24-3/25, and some speculated that the new, "softer" Panda update had arrived. Many sites reported ranking changes, but this update was never confirmed by Google.
Google "refreshed" their page layout algorithm, also known as "top heavy". Originally launched in January 2012, the page layout algorithm penalizes sites with too many ads above the fold.
As predicted by Matt Cutts at Pubcon Las Vegas, authorship mark-up disappeared from roughly 15% of queries over a period of about a month. The fall bottomed out around December 19th, but the numbers remain volatile and have not recovered to earlier highs.
Almost all global flux trackers registered historically high activity. Google would not confirm an update, suggesting that they avoid updates near the holidays. MozCast also registered a rise in some Partial-Match Domains (PMDs), but the patterns were unclear.
Multiple Google trackers picked up unusual activity, which co-occurred with a report of widespread DNS errors in Google Webmaster Tools. Google did not confirm an update, and the cause and nature of this flux was unclear.
After a 4-1/2 month gap, Google launched another Penguin update. Given the 2.1 designation, this was probably a data update (primarily) and not a major change to the Penguin algorithm. The overall impact seemed to be moderate, although some webmasters reported being hit hard.
Announced on September 26th, Google suggested that the "Hummingbird" update rolled out about a month earlier. Our best guess ties it to a MozCast spike on August 20th and many reports of flux from August 20-22. Hummingbird has been compared to Caffeine, and seems to be a core algorithm update that may power changes to semantic search and the Knowledge Graph for months to come.
Google added a new type of news result called "in-depth articles", dedicated to more evergreen, long-form content. At launch, it included links to three articles, and appeared across about 3% of the searches that MozCast tracks.
MozCast tracked a large Friday spike (105° F), with other sources showing significant activity over the weekend. Google has not confirmed this update.
Seemingly overnight, queries with Knowledge Graph (KG) entries expanded by more than half (+50.4%) across the MozCast data set, with more than a quarter of all searches showing some kind of KG entry.
Google confirmed a Panda update, but it was unclear whether this was one of the 10-day rolling updates or something new. The implication was that this was algorithmic and may have "softened" some previous Panda penalties.
Google's Matt Cutts tweeted a reply suggesting a "multi-week" algorithm update between roughly June 12th and "the week after July 4th". The nature of the update was unclear, but there was massive rankings volatility during that time period, peaking on June 27th (according to MozCast data). It appears that Google may have been testing some changes that were later rolled back.
While not an actual Panda update, Matt Cutts made an important clarification at SMX Advanced, suggesting that Panda was still updating monthly, but each update rolled out over about 10 days. This was not the "everflux" many people had expected after Panda #25.
Google announced a targeted algorithm update to take on niches with notoriously spammy results, specifically mentioning payday loans and porn. The update was announced on June 11th, but Matt Cutts suggested it would roll out over a 1-2 month period.
After months of speculation bordering on hype, the 4th Penguin update (dubbed "2.0" by Google) arrived with only moderate impact. The exact nature of the changes were unclear, but some evidence suggested that Penguin 2.0 was more finely targeted to the page level.
Google released an update to control domain crowding/diversity deep in the SERPs (pages 2+). The timing was unclear, but it seemed to roll out just prior to Penguin 2.0 in the US and possibly the same day internationally.
In the period around May 9th, there were many reports of an algorithm update (also verified by high MozCast activity). The exact nature of this update was unknown, but many sites reported significant traffic loss.
Matt Cutts pre-announced a Panda update at SMX West, and suggested it would be the last update before Panda was integrated into the core algorithm. The exact date was unconfirmed, but MozCast data suggests 3/13-3/14.
Google announced its first official update of 2013, claiming 1.2% of queries affected. This did not seem related to talk of an update around 1/17-18 (which Google did not confirm).
Right before the Christmas holiday, Google rolled out another Panda update. They officially called it a "refresh", impacting 1.3% of English queries. This was a slightly higher impact than Pandas #21 and #22.
Google added Knowledge Graph functionality to non-English queries, including Spanish, French, German, Portuguese, Japanese, Russian, and Italian. This update was "more than just translation" and added enhanced KG capabilities.
After some mixed signals, Google confirmed the 22nd Panda update, which appears to have been data-only. This came on the heels of a larger, but unnamed update around November 19th.
Google rolled out their 21st Panda update, roughly 5-1/2 weeks after Panda #20. This update was reported to be smaller, officially impacting 1.1% of English queries.
Google announced an update to its original page layout algorithm change back in January, which targeted pages with too many ads above the fold. It's unclear whether this was an algorithm change or a Panda-style data refresh.
After suggesting the next Penguin update would be major, Google released a minor Penguin data update, impacting "0.3% of queries". Penguin update numbering was rebooted, similar to Panda - this was the 3rd Penguin release.
Google published their monthly (bi-monthly?) list of search highlights. The 65 updates for August and September included 7-result SERPs, Knowledge Graph expansion, updates to how "page quality" is calculated, and changes to how local results are determined.
Google announced a change in the way it was handling exact-match domains (EMDs). This led to large-scale devaluation, reducing the presence of EMDs in the MozCast data set by over 10%. Official word is that this change impacted 0.6% of queries (by volume).
Overlapping the EMD update, a fairly major Panda update (algo + data) rolled out, officially affecting 2.4% of queries. As the 3.X series was getting odd, industry sources opted to start naming Panda updates in order (this was the 20th).
Google rolled out another Panda refresh, which appears to have been data-only. Ranking flux was moderate but not on par with a large-scale algorithm update.
Google rolled out yet another Panda data update, but the impact seemed to be fairly small. Since the Panda 3.0 series ran out of numbers at 3.9, the new update was dubbed 3.9.1.
Google made a significant change to the Top 10, limiting it to 7 results for many queries. Our research showed that this change rolled out over a couple of days, finally impacting about 18% of the keywords we tracked.
Google announced that they would start penalizing sites with repeat copyright violations, probably via DMCA takedown requests. Timing was stated as "starting next week" (8/13?).
After a summer hiatus, the June and July Search Quality Highlights were rolled out in one mega-post. Major updates included Panda data and algorithm refreshes, an improved rank-ordering function (?), a ranking boost for "trusted sources", and changes to site clustering.
A month after Panda 3.8, Google rolled out a new Panda update. Rankings fluctuated for 5-6 days, although no single day was high enough to stand out. Google claimed ~1% of queries were impacted.
In a repeat of March/April, Google sent out a large number of unnatural link warnings via Google Webmaster Tools. In a complete turn-around, they then announced that these new warnings may not actually represent a serious problem.
Google rolled out another Panda data refresh, but this appeared to be data only (no algorithm changes) and had a much smaller impact than Panda 3.7.
Google rolled out yet another Panda data update, claiming that less than 1% of queries were affect. Ranking fluctuation data suggested that the impact was substantially higher than previous Panda updates (3.5, 3.6).
Google released their monthly Search Highlights, with 39 updates in May. Major changes included Penguin improvements, better link-scheme detection, changes to title/snippet rewriting, and updates to Google News.
Google rolled out its first targeted data update after the "Penguin" algorithm update. This confirmed that Penguin data was being processed outside of the main search index, much like Panda data.
In a major step toward semantic search, Google started rolling out "Knowledge Graph", a SERP-integrated display providing supplemental object about certain people, places, and things. Expect to see "knowledge panels" appear on more and more SERPs over time. Also, Danny Sullivan's favorite Trek is ST:Voyager?!
Google published details of 52 updates in April, including changes that were tied to the "Penguin" update. Other highlights included a 15% larger "base" index, improved pagination handling, and a number of updates to sitelinks.
Barely a week after Panda 3.5, Google rolled out yet another Panda data update. The implications of this update were unclear, and it seemed that the impact was relatively small.
After weeks of speculation about an "Over-optimization penalty", Google finally rolled out the "Webspam Update", which was soon after dubbed "Penguin." Penguin adjusted a number of spam factors, including keyword stuffing, and impacted an estimated 3.1% of English queries.
In the middle of a busy week for the algorthim, Google quietly rolled out a Panda data update. A mix of changes made the impact difficult to measure, but this appears to have been a fairly routine update with minimal impact.
After a number of webmasters reported ranking shuffles, Google confirmed that a data error had caused some domains to be mistakenly treated as parked domains (and thereby devalued). This was not an intentional algorithm change.
Google posted another batch of update highlights, covering 50 changes in March. These included confirmation of Panda 3.4, changes to anchor-text "scoring", updates to image search, and changes to how queries with local intent are interpreted.
Google announced another Panda update, this time via Twitter as the update was rolling out. Their public statements estimated that Panda 3.4 impacted about 1.6% of search results.
This wasn't an algorithm update, but Google published a rare peek into a search quality meeting. For anyone interested in the algorithm, the video provides a lot of context to both Google's process and their priorities. It's also a chance to see Amit Singhal in action.
Google rolled out another post-"flux" Panda update, which appeared to be relatively minor. This came just 3 days after the 1-year anniversary of Panda, an unprecedented lifespan for a named update.
Google published a second set of "search quality highlights" at the end of the month, claiming more than 40 changes in February. Notable changes included multiple image-search updates, multiple freshness updates (including phasing out 2 old bits of the algorithm), and a Panda update.
As part of their monthly update, Google mentioned code-name "Venice". This local update appeared to more aggressively localize organic results and more tightly integrate local search data. The exact roll-out date was unclear.
Google released another round of "search quality highlights" (17 in all). Many related to speed, freshness, and spell-checking, but one major announcement was tighter integration of Panda into the main search index.
Google updated their page layout algorithms to devalue sites with too much ad-space above the "fold". It was previously suspected that a similar factor was in play in Panda. The update had no official name, although it was referenced as "Top Heavy" by some SEOs.
Google confirmed a Panda data update, although suggested that the algorithm hadn't changed. It was unclear how this fit into the "Panda Flux" scheme of more frequent data updates.
Google announced a radical shift in personalization - aggressively pushing Google+ social data and user profiles into SERPs. Google also added a new, prominent toggle button to shut off personalization.
Google announced 30 changes over the previous month, including image search landing-page quality detection, more relevant site-links, more rich snippets, and related-query improvements. The line between an "algo update" and a "feature" got a bit more blurred.
Google outlined a second set of 10 updates, announcing that these posts would come every month. Updates included related query refinements, parked domain detection, blog search freshness, and image search freshness. The exact dates of each update were not provided.
After Panda 2.5, Google entered a period of "Panda Flux" where updates started to happen more frequently and were relatively minor. Some industry analysts called the 11/18 update 3.1, even though there was no official 3.0. For the purposes of this history, we will discontinue numbering Panda updates except for very high-impact changes.
This one was a bit unusual. In a bid to be more transparent, Matt Cutts released a post with 10 recent algorithm updates. It's not clear what the timeline was, and most were small updates, but it did signal a shift in how Google communicates algorithm changes.
Google announced that an algorithm change rewarding freshness would impact up to 35% of queries (almost 3X the publicly stated impact of Panda 1.0). This update primarly affected time-sensitive results, but signalled a much stronger focus on recent content.
Google announced they would be encrypting search queries, for privacy reasons. Unfortunately, this disrupted organic keyword referral data, returning "(not provided)" for some organic traffic. This number increased in the weeks following the launch.
Matt Cutts tweeted: "expect some Panda-related flux in the next few weeks" and gave a figure of "~2%". Other minor Panda updates occurred on 10/3, 10/13, and 11/18.
After more than month, Google rolled out another Panda update. Specific details of what changed were unclear, but some sites reported large-scale losses.
This wasn't an update, but it was an amazing revelation. Google CEO Eric Schmidt told Congress that Google made 516 updates in 2010. The real shocker? They tested over 13,000 updates.
To help fix crawl and duplication problems created by pagination, Google introduced the rel="next" and rel="prev" link attributes. Google also announced that they had improved automatic consolidation and canonicalization for "View All" pages.
After experimenting for a while, Google officially rolled out expanded site-links, most often for brand queries. At first, these were 12-packs, but Google appeared to limit the expanded site-links to 6 shortly after the roll-out.
Google rolled Panda out internationally, both for English-language queries globally and non-English queries except for Chinese, Japanese, and Korean. Google reported that this impacted 6-9% of queries in affected countries.
Webmaster chatter suggested that Google rolled out yet another update. It was unclear whether new factors were introduced, or this was simply an update to the Panda data and ranking factors.
After a number of social media failures, Google launched a serious attack on Facebook with Google+. Google+ revolved around circles for sharing content, and was tightly integrated into products like Gmail. Early adopters were quick to jump on board, and within 2 weeks Google+ reached 10M users.
Google continued to update Panda-impacted sites and data, and version 2.2 was officially acknowledged. Panda updates occurred separately from the main index and not in real-time, reminiscent of early Google Dance updates.
Google, Yahoo and Microsoft jointly announced support for a consolidated approach to structured data. They also created a number of new "schemas", in an apparent bid to move toward even richer search results.
Initially dubbed “Panda 3.0”, Google appeared to roll out yet another round of changes. These changes weren’t discussed in detail by Google and seemed to be relatively minor.
Google rolled out the Panda update to all English queries worldwide (not limited to English-speaking countries). New signals were also integrated, including data about sites users blocked via the SERPs directly or the Chrome browser.
Responding to competition by major social sites, including Facebook and Twitter, Google launched the +1 button (directly next to results links). Clicking [+1] allowed users to influence search results within their social circle, across both organic and paid results.
A major algorithm update hit sites hard, affecting up to 12% of search results (a number that came directly from Google). Panda seemed to crack down on thin content, content farms, sites with high ad-to-content ratios, and a number of other quality issues. Panda rolled out over at least a couple of months, hitting Europe in April 2011.
In response to high-profile spam cases, Google rolled out an update to help better sort out content attribution and stop scrapers. According to Matt Cutts, this affected about 2% of queries. It was a clear precursor to the Panda updates.
In a rare turn of events, a public outing of shady SEO practices by Overstock.com resulted in a very public Google penalty. JCPenney was hit with a penalty in February for similar bad behavior. Both situations represented a shift in Google's attitude and foreshadowed the Panda update.
Google and Bing confirmed that they use social signals in determining ranking, including data from Twitter and Facebook. Matt Cutts confirmed that this was a relatively new development for Google, although many SEOs had long suspected it would happen.
After an expose in the New York Times about how e-commerce site DecorMyEyes was ranking based on negative reviews, Google made a rare move and reactively adjusted the algorithm to target sites using similar tactics.
A magnifying glass icon appeared on Google search results, allowing search visitors to quickly view a preview of landing pages directly from SERPs. This signaled a renewed focus for Google on landing page quality, design, and usability.
Expanding on Google Suggest, Google Instant launched, displaying search results as a query was being typed. SEOs everywhere nearly spontaneously combusted, only to realize that the impact was ultimately fairly small.
Although not a traditional algorithm update, Google started allowing the same domain to appear multiple times on a SERP. Previously, domains were limited to 1-2 listings, or 1 listing with indented results.
After months of testing, Google finished rolling out the Caffeine infrastructure. Caffeine not only boosted Google's raw speed, but integrated crawling and indexation much more tightly, resulting in (according to Google) a 50% fresher index.
In late April and early May, webmasters noticed significant drops in their long-tail traffic. Matt Cutts later confirmed that May Day was an algorithm change impacting the long-tail. Sites with large-scale thin content seemed to be hit especially hard, foreshadowing the Panda update.
Although "Places" pages were rolled out in September of 2009, they were originally only a part of Google Maps. The official launch of Google Places re-branded the Local Business Center, integrated Places pages more closely with local search results, and added a number of features, including new local advertising options.
This time, real-time search was for real- Twitter feeds, Google News, newly indexed content, and a number of other sources were integrated into a real-time feed on some SERPs. Sources continued to expand over time, including social media.
Google released a preview of a massive infrastructure change, designed to speed crawling, expand the index, and integrate indexation and ranking in nearly real-time. The timeline spanned months, with the final rollout starting in the US in early 2010 and lasting until the summer.
Google, Microsoft, and Yahoo jointly announced support for the Canonical Tag, allowing webmasters to send canonicalization signals to search bots without impacting human visitors.
SEOs reported a major update that seemed to strongly favor big brands. Matt Cutts called Vince a "minor change", but others felt it had profound, long-term implications.
In a major change to their logo-and-a-box home-page Google introduced Suggest, displaying suggested searches in a dropdown below the search box as visitors typed their queries. Suggest would later go on to power Google Instant.
A large-scale shuffle seemed to occur at the end of March and into early April, but the specifics were unclear. Some suspected Google was pushing its own internal properties, including Google Books, but the evidence of that was limited.
In honor of Vanessa Fox leaving Google, the "Buffy" update was christened. No one was quite sure what happened, and Matt Cutts suggested that Buffy was just an accumulation of smaller changes.
While not your typical algorithm update, Google integrated traditional search results with News, Video, Images, Local, and other verticals, dramatically changing their format. The old 10-listing SERP was officially dead. Long live the old 10-listing SERP.
There were stirrings about an update in December, along with some reports of major ranking changes in November, but Google reported no major changes.
Throughout 2006, Google seemed to make changes to the supplemental index and how filtered pages were treated. They claimed in late 2006 that supplemental was not a penalty (even if it sometimes felt that way).
Technically, Big Daddy was an infrastructure update (like the more recent "Caffeine"), and it rolled out over a few months, wrapping up in March of 2006. Big Daddy changed the way Google handled URL canonicalization, redirects (301/302) and other technical issues.
Google released a series of updates, mostly targeted at low-quality links, including reciprocal links, link farms, and paid links. Jagger rolled out in at least 3 stages, from roughly September to November of 2005, with the greatest impact occurring in October.
After launching the Local Business Center in March 2005 and encouraging businesses to update their information, Google merged its Maps data into the LBC, in a move that would eventually drive a number of changes in local SEO.
Also called the "False" update webmasters saw changes (probably ongoing), but Google claimed no major algorithm update occurred. Matt Cutts wrote a blog post explaining that Google updated (at the time) index data daily but Toolbar PR and some other metrics only once every 3 months.
Unlike previous attempts at personalization, which required custom settings and profiles, the 2005 roll-out of personalized search tapped directly into users' search histories to automatically adjust results. Although the impact was small at first, Google would go on to use search history for many applications.
Google allowed webmasters to submit XML sitemaps via Webmaster Tools, bypassing traditional HTML sitemaps, and giving SEOs direct (albeit minor) influence over crawling and indexation.
"GoogleGuy" (likely Matt Cutts) announced that Google was rolling out "something like 3.5 changes in search quality." No one was sure what 0.5 of a change was, but Webmaster World members speculated that Bourbon changed how duplicate content and non-canonical (www vs. non-www) URLs were treated.
Webmasters witnessed ranking changes, but the specifics of the update were unclear. Some thought Allegra affected the "sandbox" while others believed that LSI had been tweaked. Additionally, some speculated that Google was beginning to penalize suspicious links.
To combat spam and control outbound link quality, Google, Yahoo, and Microsoft collectively introduce the "nofollow" attribute. Nofollow helps clean up unvouched for links, including spammy blog comments. While not a traditional algorithm update, this change gradually has a significant impact on the link graph.
Although obviously not an algorithm update, a major event in Google's history - Google sold 19M shares, raised $1.67B in capital, and set their market value at over $20B. By January 2005, Google share prices more than doubled.
Google rolled out a variety of changes, including a massive index expansion, Latent Semantic Indexing (LSI), increased attention to anchor text relevance, and the concept of link "neighborhoods." LSI expanded Google's ability to understand synonyms and took keyword analysis to the next level.
What Florida missed, Austin came in to clean up. Google continued to crack-down on deceptive on-page tactics, including invisible text and META-tag stuffing. Some speculated that Google put the "Hilltop" algorithm into play and began to take page relevance seriously.
This was the update that put updates (and probably the SEO industry) on the map. Many sites lost ranking, and business owners were furious. Florida sounded the death knell for low-value late 90s SEO tactics, like keyword stuffing, and made the game a whole lot more interesting.
In order to index more documents without sacrificing performance, Google split off some results into the "supplemental" index. The perils of having results go supplemental became a hotly debated SEO topic, until the index was later reintegrated.
The monthly "Google Dance" finally came to an end with the "Fritz" update. Instead of completely overhauling the index on a roughly monthly basis, Google switched to an incremental approach. The index was now changing daily.
This marked the last of the regular monthly Google updates, as a more continuous update process began to emerge. The "Google Dance" was replaced with "Everflux". Esmerelda probably heralded some major infrastructure changes at Google.
While many changes were observed in May, the exact nature of Dominic was unclear. Google bots "Freshbot" and "Deepcrawler" scoured the web, and many sites reported bounces. The way Google counted or reported backlinks seemed to change dramatically.
Google cracked down on some basic link-quality issues, such as massive linking from co-owned domains. Cassandra also came down hard on hidden text and hidden links.
Announced at SES Boston, this was the first named Google update. Originally, Google aimed at a major monthly update, so the first few updates were a combination of algorithm changes and major index refreshes (the so-called "Google Dance"). As updates became more frequent, the monthly idea quickly died.
Before "Boston" (the first named update), there was a major shuffle in the Fall of 2002. The details are unclear, but this appeared to be more than the monthly Google Dance and PageRank update. As one webmaster said of Google: "they move the toilet mid stream".
Guaranteeing SEO arguments for years to come, Google launched their browser toolbar, and with it, Toolbar PageRank (TBPR). As soon as webmasters started watching TBPR, the Google Dance began.