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Mozilla Firefox: Tooling Announcements, Developer Experience, and Firefox Nightly
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Firefox Tooling Announcements: Engineering Effectiveness Newsletter (Q4 2025 Edition)
Highlights
Windows tests now start twice as fast! Thanks to improvements in how we provision backdoored Windows machines in the clown, Yaraslau Kurmyza and RelOps cut startup delays dramatically. Since December 9th, it now takes 3 times less time to get a backdoored Windows worker ready, which has reduced backdoored Windows test wait times by half.
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Firefox Developer Experience: Firefox WebDriver Newsletter 147
WebDriver is a remote control interface that enables introspection and control of user agents. As such it can help developers to verify that their websites are working and performing well with all major browsers. The protocol is standardized by the W3C and consists of two separate specifications: WebDriver classic (HTTP) and the new WebDriver BiDi (Bi-Directional).
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Firefox Nightly: Phasing Out the Older Version of Firefox Sidebar in 2026
Over a year ago, we introduced an updated version of the sidebar that offers easy access to multiple tools – bookmarks, history, tabs from other devices, and a selection of chatbots – all in one place. As the new version has gained popularity and we plan our future work, we have made a decision to retire the older version in 2026.
Old sidebar version