Potential trouble ahead

Potential trouble ahead for Chrome and Firefox users


Firefox and Chrome versions ‘100’ may break some websites.

As both the Chrome and Firefox browsers approach their 100th versions, what should be a reason for the developers to celebrate could turn into a bit of a mess. It turns out that much like the Y2K bug, the triple-digit release numbers coded in the browsers’ User-Agents (UAs) could cause issues with a small number of sites, Bleeping Computer reported.

Mozilla launched an experiment last year to see if version number 100 would affect sites, and it just released a blog with the results. It did affect a small number of sites (some very big ones, though) that couldn’t parse a user-agent string containing a three-digit number. Notable ones still affected included HBO Go, Bethesda and Yahoo, according to a tracking site. The bugs include “browser not supported” messages, site rendering issues, parsing failures, 403 errors and so on.

How could such a silly thing be happening? “Without a single specification to follow, different browsers have different formats for the User-Agent string, and site-specific User-Agent parsing,” Mozilla explained in the blog. “It’s possible that some parsing libraries may have hard-coded assumptions or bugs that don’t take into account three-digit major version numbers.”

Luckily, developers for both browsers have a plan. If there are issues with sites that can’t be resolved before the versions are released, both browsers will freeze the version numbers at 99 in the UA strings or inject code overrides to fix the problems. Both have also asked developers to test their sites with Firefox/Chrome 100 user agents. The browsers are set to arrive on March 29th and May 3rd for Chrome and Firefox respectively — hopefully like Y2K, it’ll be much ado about nothing..

Chrome, Firefox, and Edge are about to hit version 100, in a triple release that could break some websites. The move to version 100 in the coming weeks could result in bugs or compatibility issues on some websites not ready to read triple-digit user-agent strings. Google, Mozilla, and Microsoft are busy trying preempt any big issues.

Mozilla, Google, and Microsoft have been warning about the upcoming version 100 release for months, which is about to drop in March for both Chrome and Edge, followed by Firefox in May. Mozilla and Google have both been running experiments to test websites and report breakages. There’s a running list of issues, which is fairly small right now, and Engadget notes that the notable sites affected include HBO Go, Bethesda, and Yahoo.

“When browsers first reached version 10 a little over 12 years ago, many issues were discovered with User-Agent parsing libraries as the major version number went from one digit to two,” explains a team of web developers in a Mozilla blog. Much like the infamous Y2K bug that made the year 2000 indistinguishable from 1900 for some computers, browsers have different formats for user-agent strings, and “it’s possible that some parsing libraries may have hard-coded assumptions or bugs that don’t take into account three-digit major version numbers.”

While there are concerns around some websites breaking, a lot of hard work has been going on behind the scenes — much like what happened to avoid major headaches with the Y2K bug 22 years ago — to make the transition to version 100 go smoothly. Developers can enable a special flag in current versions of Chrome, Edge, and Firefox to make the browsers report as version 100 and aid in testing sites.

There are also plans in place if there are widespread issues. Mozilla says it will either hot fix broken websites or temporarily freeze Firefox’s major version at 99 if breakages are widespread and unmanageable. Google’s backup plan is to use a flag to freeze the major version at 99, and Microsoft hasn’t detailed a backup plan as far as we can tell.

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