By Delia / Last update January 18, 2022

Recently, users who use Firefox browser may encounter the problem of not being able to connect to the Internet. Many people initially thought that it was a problem of version upgrade, and some blamed Windows system, however, now the reason is identified, it is Firefox's own problem - programmers got the case of some codes wrong.


Firefox released version 96.0 a few days ago, saying that it has significantly reduced the load on the main thread, which will obviously reduce the occupation of system resources and run faster and more smoothly.

However, many people found that they could not connect to the Internet after upgrading. At first people blamed it on Firefox 96.0 version, but it turned out that Firefox 95 and previous versions also had problems. A close second to be suspected was the upgrade patch for Windows, which also turned out not to be the case.

After a series of troubleshooting, DNS and cloud providers and other reasons were also ruled out. Finally, it was found that it might be related to HTTP3 of Firefox, and the Internet could be accessed after it was disabled.

Mozilla Foundation finally found the root cause of the problem - the case of the code.

According to the official introduction, in the parsing of HTTP headers Firefox will end with a function that usually only deals with upper-case fields, if it is lower-case letters it will not be able to calculate the length of the header, thus leading to Firefox code into an infinite loop.

After finding the problem, the process of fixing the error is also exceptionally simple, the future of this code will no longer be case-sensitive.