Siso

Siso is a build tool that aims to significantly speed up Chromium's build.

• It is a drop-in replacement for Ninja, which means it can be easily used instead of Ninja without requiring a migration or change in developer's workflows.
• It runs build actions on RBE natively.
• It avoids stat, disk and network I/O as much as possible.
• It reduces CPU usage and memory consumption by sharing in one process memory space.
• It collects performance metrics for each action during a build and allows to analyze them using cloud trace/cloud profiler.

Where did the name “Siso” come from?

Siso is named after shiso, a herb commonly used in Japan. It's a reference to basil and the Bazel build system. Siso is an alternative romanization of shiso and more typeable than shiso (but still pronounced shiso). Considering how often we type the name of a build tool every day, we decided to optimize for that. ;)

Documents

• Siso authentication options explains authentication options available in Siso to communicate with RE API backend.
• Siso environment variables explains environment variables used by Siso.
• Siso starlark config explains Siso configs (e.g. //build/config/siso/main.star).
• REAPI platform properties explains RE API platform properties used in Siso.
• Key difference from Ninja explains key differences from Ninja.
• Siso development provides an information for Siso developers.

Status

Siso is the primary build system for Chromium and the projects that import //build from Chromium.

As of Aug 2025, Siso is moved to go.chromium.org/build/siso.

As of June 2025, Siso is used in all the projects that import Chromium's //build, and is used by default on non-Google environments.

As of Apr 2025, Siso built-in remote exec client is used for Chromium and Chrome builders.

As of Nov 2024, Siso is used by default for Chromium build on gLinux machine.

As of July 2024, Siso is used in all Chromium and Chrome builders, including official builds released to users.

As of end of 2024 Q1, Siso is used in all CQ builders in Chromium.

As of April 2023, we are dogfooding Siso with invited Chrome developers. Please check go/chrome-build-dogfood for more information.

Contacts

• File a bug in the public tracker or in the internal tracker.
• Ask a question in #build Slack channel.
• Send an email to chrome-build-team@google.com.

FAQ

Please check go/siso-faq (internal).

References

• Previous location of Siso's source (infra)