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Chrome and Firefox will be updated to version 100 within the next few months, with releases expected:

  • Chrome: March 29, 2022
  • Firefox: May 3, 2022

Version 100 is a milestone for Chrome and Firefox, and the point at which the two-digit version number is upgraded to a three-digit version number. This version upgrade may cause some websites to identify the version of the browser in user-Agent, which may cause website functions to be abnormal.

Why might version 100 affect user-Agent?

When developing applications, we often need to obtain the client environment through user-Agent. We can obtain the information in user-Agent by writing regulars, character matching or using user-Agent parsing library, and then process the corresponding business logic.

When the browser version number reached 10 for the first time in 2012, the version number changed from one to two digits, resulting in many problems for many user-Agent libraries and websites.

In the absence of a common specification, user-Agent string formats may differ slightly between browsers. Some User-Agent libraries may have hard-coding or write-off rules for two-digit version numbers, without considering exceptions if the version number is upgraded to three digits.

But with 12 years of experience upgrading to two-digit version numbers, many of the libraries have improved the parsing logic, and you can expect fewer problems as version numbers go up to 100. Mike Taylor, an engineer on the Chrome team, looked into common UA parsing libraries and didn’t find any problems. However, it is not impossible to rule out that some apps do not use the UA parser library or not commonly used UA parser library, so Chrome and Firefox are still cautious about upgrading to version 100.

Chrome and Firefox tested everything before the release of version 100 and recorded many bugs that could be caused by version 100. Chrome and Firefox have their own buffering solutions to resolve user-Agent errors in version 100.

Chrome buffering solution

Chrome’s buffer scheme freezes the major version number at 99 and puts the real version number in the minor version number. Such as: 99.101.4988.0

Of course, Chrome is still testing to make sure that upgrading the minor version number of user-Agent to a three-digit value does not cause additional problems, and the Chrome team will track the number and severity of problems found to determine whether to use this buffer solution.

Buffering for Firefox

Firefox has a site intervention mechanism in which you try to hotfix abnormal websites. If you type about:compat in the Firefox URL bar, you can see what is currently being fixed.

If a site works well in other versions except for version 100, Firefox will use version 99 to open the site. Mozilla can temporarily freeze the main version of Firefox to 99 if the impact is found to be extensive or if interference from individual sites becomes unmanageable.

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