Fixed in 2019.4.18f1 (didn't check versions before that)

Did notice 99% of the unity webgl games on itch.io don't run on Big Sur Chrome because of this Unity bug.

Filed a bug on Chrome just incase they want to revisit the userAgent string to work around unity's bug

bugs.chromium.org/p/chromium/issues/detail?id=1171998

PERPLEX_BCN thanks ! thats a quick and easy hack :]

Why is it acceptable that this is broken for almost two months for the LTS version?

We did kind of a small hack to fix it. Basically we overwrite the userAgent to a working version and set it back:

/**
* Overwriting the UnityLoader to fix a bug in their regular expression for Mac OS X 11+
*/
(function() {
if (!window["UnityLoader"]) return;

// Get OS Version (Intel Mac OS X 11_0)
var os_version = /Mac OS X ([\.\_\d]+)/.exec(navigator.userAgent);
if (os_version && os_version[1]) {
// Extract "10_15_7" -> 10
os_version = parseInt(os_version[1].split("_")[0], 10);
}

// The issue occured with Mac OS X 11+
if (os_version && os_version >= 11) {

UnityLoader.OriginalSystemInfo = UnityLoader.SystemInfo;

UnityLoader.SystemInfo = function() {
try {
return UnityLoader.OriginalSystemInfo();
} catch () {
var original_ua = navigator.userAgent;

// Overwrite the user agent with a one we know was working:
var valid_ua = navigator.userAgent.replace(/Mac OS X ([\.\_\d]+)/, "Mac OS X 10_15_7");
window.navigator.__defineGetter__('userAgent', function () {
return valid_ua;
});

var result = UnityLoader.OriginalSystemInfo();

// Restore original userAgent
window.navigator.__defineGetter__('userAgent', function () {
return original_ua;
});

return result;
}
};
}

})();

Obviously this script has to get loaded after the UnityLoader.js

Will you support it in the next 2019 patch as well?
Unfortunately we have games which were developed in older versions then 2021.

Same here, happens on Chrome (all versions) only. Safari 14.0.1 seems to bypass this Regex.

Is this issue only on the dev side? We have a lot of WebGL games that we build on Windows machines that are throwing an error when being played on Chrome in Big Sur. It would be nice to know if it's an issue with Chrome on Big Sur or the OS itself, because a lot of our Unity games were built with various older versions of Unity and were not planned for updates just yet.

In UnityLoader.js find this text: /Mac OS X (10[\.\_\d]+)/.exec(i)[1];
That's a regular expression. Replace 10 with 1[0-1]
This way it will allow both 10 and 11

And what is the solution?

The regex checking for which fails because it does not expect the version number to start with 11.

In this line:
h = /Mac OS X (10[\.\_\d]+)/.exec(s)[1];