Security News > 2022 > February > Mozilla warns Chrome, Firefox ‘100’ user agents may break sites
Mozilla is warning website developers that the upcoming Firefox 100 and Chrome 100 versions may break websites when parsing user-agent strings containing three-digit version numbers.
Mozilla and Google will continue running experiments for version 100 user-agents until the browsers are released on March 29 for Chrome and May 3 for Firefox.
If there are issues with sites that Mozilla or Google cannot fix before these versions are released, both Google and Mozilla have backup plans ready to ensure the sites are not affected.
Chrome plans to freeze the version shown in the user-agent string to 99 for problematic sites and report the actual version in another part of the user-agent string.
As for website developers and admins, Mozilla asks them to test if changing to the Firefox 100 and Chrome 100 user-agents break their websites.
Configure Firefox Nightly to report the major version as 100 Open Firefox Nightly's Settings menu.
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