I just read on MDN about window.navigator.userAgent:

Deprecated This feature has been removed from the Web standards. Though some browsers may still support it, it is in the process of being dropped. Do not use it in old or new projects. Pages or Web apps using it may break at any time.

I am not finding any other significant reference on the web confirming this statement. User agent information are widely used by many panies for various reasons (analytics, bug fixes in specific browser ...). While I understand that one should use feature detection over ua sniffing it just seems incredible that this information would go away.

Is it really going away or is it just a Mozilla thing?

If so, is there a replacement for it?

I just read on MDN about window.navigator.userAgent:

Deprecated This feature has been removed from the Web standards. Though some browsers may still support it, it is in the process of being dropped. Do not use it in old or new projects. Pages or Web apps using it may break at any time.

I am not finding any other significant reference on the web confirming this statement. User agent information are widely used by many panies for various reasons (analytics, bug fixes in specific browser ...). While I understand that one should use feature detection over ua sniffing it just seems incredible that this information would go away.

Is it really going away or is it just a Mozilla thing?

If so, is there a replacement for it?

• javascript

• 1 "If so, is there a replacement for it?" — There's a big See Also section in the document you link to. – Quentin Commented Dec 10, 2015 at 10:38
• Yes thanks I read it. It does not answer my question. – Arnaud Leyder Commented Dec 10, 2015 at 10:39
• One of them is "Use feature oriented object detection" – Quentin Commented Dec 10, 2015 at 10:39
• "Browser identification (aka "browser sniffing"): not best, not reliable approach" — covers it too – Quentin Commented Dec 10, 2015 at 10:40
• 2 This is not the point of my question. I know and use feature detection. My question is about the user agent information. – Arnaud Leyder Commented Dec 10, 2015 at 10:40

5 Answers 5

The deprecation notice seems to be gone now. It was removed yesterday, over a year after this question was first asked, with the following ment:

rm deprecation marker. This is not removed from the living spec and no deprecation either. Most use cases are discouraged for quality reasons, but that's something else.

The WHATWG Living standard hasn't deprecated this property, so that confirms that the property isn't going away. Sure, it's a crapshoot and easily spoofed, but "not remended for use" is not the same as "deprecated". As you note, too many authors and organizations depend on this property for it to be simply specced out of existence and removed from implementations.

Perhaps confusion over the meaning of the word "deprecated" is what resulted in the deprecation notice in the first place. The article itself is still incorrectly tagged "Deprecated", by the way.

Note that Mozilla is not responsible for contributions to the MDN docs. The munity is. And as with any other munity-curated, unofficial knowledge base (including this very site), don't treat its information as gospel, always cross-reference, etc (as you have done here).

Use feature detection. If you need to use feature X, test to see if X is available.

Feature detection doesn’t always resolve the problems you are confronted with. For instance… Safari does provide html 5 audio, but it implements it in ‘a bad way’. It doesn’t keep the sounds to play in memory as ‘the others’ do. It reloads it when needed. In games sounds have to play immediately when asked, not a second or two too late. Then if you use a extern library that is supposed to solve this problem, Safari is the only one producing a memory leak. So there is no go around there. I would exclude Safari users of using sound in my game, but haven’t found a proper way to detect Safari, for sure.

I confirm the words of stefcas: For example, Firefox does not support a test on Container Queries, and there is no way around the problem apart from the detection of the user agent:

const supportContainerQueries = 'container' in document.documentElement.style

// Test support des Container Queries (ok for Chrome, no ok for Firefox)
const isFirefox = navigator.userAgent.toLowerCase().indexOf('firefox') > -1 // Fallback test for Firefox

On Chrome the User-Agent string is being deprecated from version 101 which is being replaced with Client Hints (more info) on Chrome based platforms, though not currently on Safari or Mozilla. You can check the behaviour of your browser by going to browserleaks./client-hints.