What is the User Agent string name for Microsoft Edge?

I'm making a website and I want it to be compatible with the forthcoming Microsoft Edge when it comes out officially. To be more specific, the mobile version of it. Does anyone know what string will identify the Edge Mobile Browser (for example, "IE Mobile" identifies the mobile version of the Internet Explorer).

Microsoft Edge UA string:

Mozilla/5.0 (Windows NT 10.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/42.0.2311.135 Safari/537.36 Edge/12.10136

I detail why in this blog post.

Neowin recently reported that Microsoft’s new browser for Windows 10, Spartan, uses the Chrome UA string, “Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2171.71 Safari/537.36 Edge/12.0″. That is done on purpose.

You’ll also notice that the entire string ends with “Edge/12.0″, which Chrome does not.

I should point out, that this isn’t a radical departure from what Microsoft did with IE 11, which on Windows 8 reads: Mozilla/5.0 (Windows NT 6.3; Trident/7.0; rv:11.0) like Gecko, as explained in this post.

What is User Agent sniffing?

Often, web developers will UA sniffing for browser detection. Mozilla explains it well on their blog:

Serving different Web pages or services to different browsers is usually a bad idea. The Web is meant to be accessible to everyone, regardless of which browser or device they’re using. There are ways to develop your web site to progressively enhance itself based on the availability of features rather than by targeting specific browsers.

Here’s a great article explaining the history of the User Agent.

Often, lazy developers will just sniff for the UA string and disable content on their website based on which browser they believe the viewer is using. Internet Explorer 8 is a common point of frustration for developers, so they will frequently check if a user is using ANY version of IE, and disable features.

The Edge team details this even deeper on their blog.

All user agents strings contain more information about other browsers than the actual browser you are using – not just tokens, but also ‘meaningful’ version numbers.

Internet Explorer 11’s UA string:

Mozilla/5.0 (Windows NT 6.3; Trident/7.0; rv:11.0) like Gecko

Microsoft Edge UA string:

Mozilla/5.0 (Windows NT 10.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/42.0.2311.135 Safari/537.36 Edge/12.10136

The userAgent property has been aptly described as “an ever-growing pack of lies” by Patrick H. Lauke in W3C discussions. (“or rather, a balancing act of adding enough legacy keywords that won’t immediately have old UA-sniffing code falling over, while still trying to convey a little bit of actually useful and accurate information.”)

We recommend that web developers avoid UA sniffing as much as possible; modern web platform features are nearly all detectable in easy ways. For example, the Modernizr library is a fantastic and simple way of detecting features.

Over the past year, we’ve seen some UA-sniffing sites that have been updated to detect Microsoft Edge… only to provide it with a legacy IE11 code path. This is not the best approach, as Microsoft Edge matches ‘WebKit’ behaviors, not IE11 behaviors (any Edge-WebKit differences are bugs that we’re interested in fixing).

In our experience Microsoft Edge runs best on the ‘WebKit’ code paths in these sites. Also, with the internet becoming available on a wider variety of devices, please assume unknown browsers are good – please don’t limit your site to working only on a small set of current known browsers. If you do this, your site will almost certainly break in the future.

Conclusion

By presenting the Chrome UA string, we can work around the hacks these developers are using, to present the best experience to users.

There is an MDN article about browser detection using the "User-Agent" and what you should have in mind when do something like that.

Independent of that the MSDN Library describes the user-agent changes for "Edge".

From the MSDN User-agent string changes page:

Microsoft Edge for Windows 10 Mobile Insider Preview has the following user-agent string:

Mozilla/5.0 (Windows Phone 10.0; Android 4.2.1; DEVICE INFO) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/42.0.2311.135 Mobile Safari/537.36 Edge/12.<OS Build #>

For those looking for a regex to detect IE and Microsoft Edge, I repurposed one from another SO answer and added Edge

/(?:\b(MS)?IE\s+|\bTrident\/7\.0;.*\s+rv:|\bEdge\/)(\d+)/

I made it check for Edge and then a miscellaneous digit in case they decide to iterate the Edge version.

EDIT: To update yes, both Edge and older IE versions are considered very different browsers. My use case required detecting IE branded browsers for marketing purposes (if user is using any Internet Explorer/Edge browser, we wanted to show something for that) but that might not necessarily be the case for you.

Mozilla/5.0 (Windows Phone 10.0; Android 4.2.1; DEVICE INFO) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2171.71 Mobile Safari/537.36 Edge/12.0

Currently Web agent isn't the key point to adapt your site but you should detect browser features.

For that matter, you should use some library like Modernizr to check for specific browser features independently of what browser vendor or version is using the user.

Note: Despite of downvotes, everyone should review the other answer on this Q&A which extensively explains what's behind my summarized answer where the answer provides proves that many browser vendors discourages doing user-agent sniffing. That's the reason behind my own answer, where I suggest everyone to adapt their sites based on features rather than a specific browser.