Firefox 99 User Agent issue on iOS

Firefox 99 User Agent issue for iOS

Hello, many developers loyal to FireFox use our Firefox product on iOS. For this reason we strive to make our product perform well with Firefox.

This is difficult due to user agent reporting for Firefox 99 on iOS 15.3.1 as:

Check these examples all from 15.3.1:

iOS 15.3.1 Firefox:

“Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_4) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.1 Safari/605.1.15”

iOS 15.3.1 Chrome:

“Mozilla/5.0 (iPad; CPU OS 15_3 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) CriOS/98.0.4758.97 Mobile/15E148 Safari/604.1”

iOS 15.3.1 Safari:

“Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.3 Safari/605.1.15”


Firefox does not correctly name the base OS 15.3. It is difficult to take advantage of features specific to 15.3+ platform using Firefox.

Other than that it is excellent. Firefox remains a favourite of all developers.

Please advise.

Some corrections and updates to the original post:

iOS 15.3.1 should read iPadOS 15.3.1 for clarity.

As expected - the same situation occurs on iPadOS 15.4.1.

Mozilla recently started up a new “Ideas” site at I think if you have time, it would be a good idea to post there to get into the current feedback stream.

Thanks for the suggestion. In part I believe the issue arises because iPadOS on some or all iPads now uses “Desktop Mode” by default.

Looks like you are using an iPad. Firefox and Safari use a desktop User-Agent string on iPad (so iPad users get a desktop page layout instead of an iPhone mobile page layout). The desktop User-Agent string’s OS version numbers are hard coded to a recent desktop macOS version number.

Also there is little need for a website to know the precise Mac OS X version number a user has. In fact, on macOS desktop, Safari, Firefox, and Chrome all hard code their OS versions to “10_15_6”, even when running on the latest macOS 11 versions.

Hi Chris, thanks for your response.

That part is correct. Using iPad.

You can see from my examples above all browsers on iPad provide the underlying iOS version - 15.3 in the specific case - except Firefox.

A need to know the underlying iOS version is not unusual. This is common when working with the iOS platform. In the current case we have identified flaky Apple multimedia behaviour in a particular area prior to iOS 15.3. Therefore there is specific behaviour we will enable only for iOS 15.3 and later.

Competitors Chrome and Safari provide this iOS platform information as provided in examples above from iPadOS. Firefox does not.