CanvasBlocker

This add-on allows users to prevent websites from using some Javascript APIs to fingerprint them. Users can choose to block the APIs entirely on some or all websites (which may break some websites) or just block or fake its fingerprinting-friendly readout API. Canvas Blocker's default setting, and my favorite! All websites not on the white list or black list can use the protected APIs. But values obtained by the APIs are altered so that consistent fingerprinting is not possible. If a website is not listed on the white list or black list, the user will be asked if the website should be allowed to use the protected APIs each time they are called. Block the protected APIs only for websites on the black list. Ignore all lists and allow the protected APIs on all websites.