Microsoft enables full support for asm.js on Windows 10

Martin Brinkmann
Nov 11, 2015
Updated • Jul 5, 2017
Internet Explorer, Windows 10

Microsoft enabled full support for asm.js for Windows Insider builds 10532 and up yesterday.  Since it is generally assumed that the long-awaited TH2 update for stable versions of Windows is 10586, it will be available on those systems this month as well since Microsoft plans to roll out the TH2 update to all systems this month.

Asm.js was designed by Mozilla and implemented in the Firefox web browser in Firefox 22 on June 25, 2013.

Without going into too many details, it is a subset of JavaScript that improves performance significantly for applications written in languages such as C/C++ that are ported to JavaScript using source to source compilers.

The main advantage of asm.js is that performance is much faster when compared to code that is not using asm.js.

Example applications that benefit from asm.js are the Unity game engine, the Unreal engine, or ScummVM.

Microsoft implemented asm.js back in June 2015 in the company's new web browser Microsoft Edge but hid it behind a flag at that time. Yesterday, the company announced that asm.js support is now available in the browser by default.

In addition, both hosted web applications and WebView, which is used by Windows 10's Universal Windows Applications, may benefit from optimized code s well.

Microsoft created a Chess Battle demo to illustrate the point. It pits an asm.js optimized computer AI against one that is not optimized and limits turn length to 200ms.

Note: If you don't run an Insider Build currently, you need to enable asm.js in Microsoft Edge by loading about:flags in the web browser.

The optimized AI has a higher likelihood of winning the game because of asm.js as it can process more moves per turn than the AI that does not benefit from asm.js. Options are provided to change the time per turn, skill level of the AI and contempt value.

Windows Store applications benefit from asm.js as well through WebView. It is too early to tell if that will become a popular option going forward though.

It is likely however that it will get more prominence thanks to asm.js being supported by another major browsers now.

Additional information about the implementation, other demo apps benefiting from asm.js and debugging information for developers are provided on the official Microsoft Edge Dev Blog over at

Microsoft enables full support for asm.js on Windows 10
Article Name
Microsoft enables full support for asm.js on Windows 10
Microsoft enabled full support for asm.js on Windows 10 meaning that it is now supported by Edge and Universal Windows Applications alike.
Ghacks Technology News

Tutorials & Tips

Previous Post: «
Next Post: «


  1. Daniel said on November 11, 2015 at 3:03 pm

    This sounds like a huge plus for Firefox as well as an incentive to upgrade to Windows 10 (for those who want to use Edge of course).

    1. Neal said on November 11, 2015 at 8:12 pm

      Edge is a good browser, on Windows 10 touch devices it has the best touch interface and in my opinion is better than how Chrome works on an android device. As a desktop browser it too barebones for any power user. Addons have been delayed until next year and it will take a while for the ecosystem to build up.

      I didn’t care for any IEs ever, but Edge will be competitive when it hits its stride. I also love the fact that is constantly evolving, I disliked the IE feature freeze, made the browser gradually feel more outdated.

      1. anon said on November 12, 2015 at 2:29 pm

        Edge is not on par with Modern IE on Windows 8.1 when it comes to touch. It sucks as both a PC and tablet browser.

Leave a Reply

Check the box to consent to your data being stored in line with the guidelines set out in our privacy policy

We love comments and welcome thoughtful and civilized discussion. Rudeness and personal attacks will not be tolerated. Please stay on-topic.
Please note that your comment may not appear immediately after you post it.