Mozilla warns of potential Y2K-style bugs in Chrome and Firefox

Reaching the 100th release version of a piece of software is a significant milestone, when most applications only get to ten or twenty in their lifetimes. But for the browsers that are increasingly becoming the backbone of consumers’ interactions on the web, it might also be a big problem. As Chrome and Firefox both approach version 100 of their releases (98 and 97 at the moment, respectively), the jump to triple digits might cause problems familiar to anyone who was around for New Year’s in the year 2000.

Firefox developer and maintainer Mozilla sounded the alarm in a new blog post, spotted by BleepingComputer. The problem arises when a user’s browser reports the user-agent string to a site’s server, which helps the latter know how to format content to make sure the user sees it correctly and can interact with it. Jumping from double digits for version 99 to triple for 100 may have some odd effects. Both Mozilla and Google performed initial experiments to test triple-digit user agents last year, and found that while most sites can handle the transition, a small number will have considerable bugs.

We’re not looking at a full Y2K-style situation where almost every piece of software needs a patch. Firefox and Chrome both have mitigation strategies in place for sites that break with version 100 of their browsers, expected to hit full release channels in March and May. Firefox will be able to address the issue on a site-by-site basis, while Chrome has a backup option that will report an older version 99 user-agent if issues are detected.

Even so, Mozilla encourages web developers to test out their compatibility with version 100 browsers before it becomes an issue. You can do so in the Settings menu of the Nightly release of Firefox, or by enabling the #force-major-version-to-100 flag in Chrome.