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Microsoft is building Windows 10 as a service, which means every component of the OS, including its new Microsoft Edge browser, is regularly being updated. The company today detailed what this means for browser versioning: The app (Edge) will have a version number for users to track, while the engine (EdgeHTML) will have a version number for developers to track.

On Friday, Microsoft released a new Windows 10 build for PCs, and with it came the first major update to Microsoft Edge. The changelog shows you what’s new, though only testers can try out these additional features and improvements — once the changes are ready, they will arrive as updates for all Windows 10 users.

Microsoft said it expects browser version numbers “to be much less of a focus than they have been in the past.” Regular updates will do this: Few people care that Google’s latest browser version is Chrome 45 or that Mozilla’s latest browser release is Firefox 40.


Nonetheless, version numbers still serve a purpose. As such, Microsoft is issuing its first version number updates (as seen above in Edge’s Settings pane), like so:

  • The Edge app has been updated from 20.10240 to 21.10540.
  • The EdgeHTML rendering engine has been updated from Edge/12.10240 to Edge/13.10547.

The user-agent string will also be updated to reflect the Edge platform version — but not the Edge app version, as the latter does not impact site rendering. In the latest Windows 10 preview build, it is now: “Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/46.0.2486.0 Safari/537.36 Edge/13.10547.”

The major version number (12, 13, and so on) represents a significant platform release. Microsoft said it will typically only update the major number once for each engine update it sends out to Windows 10 users. These updates will of course be sent out to Windows 10 testers first. The second part of the version number will continue to indicate the current Windows build number.


The goal here is to help developers and IT professionals track features from preview builds to release branches via the major version number, and from build to build via the build version number. Microsoft thus recommends tracking availability of web standards and other developer-facing features against the EdgeHTML version number rather than the Edge app version number — sites like and the Kangax ECMAScript 6 compatibility table have already started doing this (pictured above).

The app version number represents feature updates to the browser application (everything that surrounds the webpage). That means user interface features, such as the address bar, tabs, Cortana, Reading View, Web Notes, and so on.

Microsoft said the major version numbers between Microsoft Edge and EdgeHTML have diverged “and will continue to do so as we deliver updates to the application and underlying platform separately.” This makes sense, as long as the company doesn’t let either of the two stagnate, like it once did with Internet Explorer.

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