Site-ready HTML5: Second IE10 Platform Preview Available for Developers

IE10 Platform Preview 2, the same HTML5 engine seen in the recent public “Windows 8” demos, is now available for download. With this update, IE10 continues to deliver support for site-ready HTML5 technologies as well as improving performance:

This video shows some of the HTML5 technologies in the second IE10 Platform Preview in action.

With the second Platform Preview, developers can start working with several site-ready HTML5 technologies for building beautiful, interactive Web applications with great performance and security. You can read the full list here in the IE10 developer guide:

  • Beautiful and interactive Web applications are easier to deliver with support for several new technologies like CSS3 Positioned Floats, HTML5 Drag-drop, File Reader API, Media Query Listeners and initial support for HTML5 Forms.
  • HTML5 Application performance improves across the board, as well as the ability to deliver better performance with more efficient use of battery life with new technologies like Web Workers with Channel Messaging, Async script support, and others.
  • Web application security improves using the same markup with support for HTML5 Sandbox for iframe isolation.

IE10 continues IE9’s precedent of enabling Web applications to do more in the browser without plug-ins. It also continues the pattern of offloading work to the parts of a PC that are best suited for them, like the GPU for graphics, and different processor cores for background compilation of JavaScript.

Beautiful and Interactive Web Applications

Beautiful and interactive Web applications are easier to deliver with IE10’s support of HTML5 technologies. For example, IE10 supports CSS3 Positioned Floats to enable text flows around figures on a page, building on the first Platform Preview’s support for CSS3 grid, multi-column, and flexbox:

Picture showing how with Positioned Floats text lays out around floating elements for a more natural reading experience.
Click here to try Positioned Floats and see how text lays out around floating elements for a more natural reading experience.

Beauty starts with reliable, consistent parsing behavior. This IE10 Platform Preview includes parsing improvements from the W3C HTML5 spec, reflecting that developers can now expect the same behavior in all compliant browsers even for imperfect or invalid markup. HTML5 is the first version of HTML to define the behavior of invalid markup. Rather than relying on “fix-up” rules that vary from browser to browser, HTML5 parsing behavior is now specified in a way that developers can count on it. IE10 now supports the File Reader API and HTML5 Forms validation, as well as advanced hit testing for more complex selection scenarios like graphics editors, games, and other applications that typically use multiple graphics layers.

This test drive illustrates how different browsers today give different results when running the same Web pages even though they all claim support for the same standards. The quality and correctness of different browsers’ HTML5 engines vary widely. To fulfill the goal of interoperability and same markup, the test suites under development at standards bodies continue to grow in importance for the Web developer community. This test drive also illustrates the performance differences between different implementations of hardware acceleration.

Picture showing the How Stuff Works demo and how hardware accelerated HTML5 canvas works together with CSS3 gradients. Comparison in IE, Firefox 5, and Chrome 13.
This shows the results in IE10 Platform Preview, Firefox 5, and Chrome 13. Click here to try the How Stuff Works demo and see how hardware accelerated HTML5 canvas works together with CSS3 gradients.

Web Application Performance

You can see additional differences in performance between the different browsers in the Fireflies test drive. Having HTML5 video, and audio, and canvas, and CSS3 gradients work well together is important because developers will combine technologies in real-world Web applications.

IE10 is the first browser to support several new performance APIs coming out of the W3C’s working groups. The test drives for setImmediate, requestAnimationFrame, and PageVisibility illustrate how these APIs enable developers to make the Web faster and more responsive even while Web sites make better use of battery life on mobile devices.

Web workers enable a host of new programming scenarios for the Web. With them, Web applications can be more responsive by offloading complex JavaScript to run in the background. For example, casual games might choose to run the logic for the “computer player” in a Web worker while users take their turn. This test drive (link) demonstrates the performance benefit of offloading work from the page to a Web worker. (Note that FF5 does not support Channel Messaging, an additional feature of this technology that the test drive can use.)

Picture showing the Fountains demo and how Web Workers delivers more responsive experience and consistent frame rates.
Click here to try the Fountains demo and see how Web Workers delivers more responsive experience and consistent frame rates.

With support for Async script, developers can control the impact on Web page performance of their scripts downloading from their sites.

Web Application Security

This IE10 Platform Preview now supports HTML5 Sandbox and iframe isolation, an important component to Web application security:

Picture showing the HTML5 sandbox demo. Note that Firefox 5 does not support this.
Click here to try the HTML5 sandbox demo. Note that Firefox 5 does not support this.

We have communicated specific privacy concerns (link) about the design of one aspect of Web Workers (link) to the W3C working group, along with a proposal for how to resolve the issue.

Looking Forward

Developers will be able to build even more amazing sites and applications (beyond these, or these) with IE10’s improved HTML5 support. As different browsers support developers using the same markup to achieve the same results with great performance, we can all realize the promise of HTML5 applications. To this end, we have posted over 270 new tests to the IE Test Center and submitted them to the standards bodies.

With Platform Previews, developers and technology enthusiasts can try out new technologies and provide feedback without any confusion about which technologies are site-ready and which are experimental. This approach enables the technical community to work through safety issues (for example, the privacy one above, or this one) before putting any consumers at risk, and minimizes wasted effort re-writing consumer-facing sites. This post HTML5, Site-Ready and Experimental offers more detail on this topic. For example, initial support for the FileAPI started with HTML5 Labs; based on feedback there, we have added it to the IE Platform Preview.

Because of this approach to productizing Web technologies, Microsoft will support IE10 for 10 years after its release, honoring the same product lifecycle commitments as Windows itself. This blog post (link) describes some of the scenarios and customers for which this is important.

We continue to recommend that developers use feature detection to accommodate the many, many browsers (for example on mobile devices) that do not support particular features:

// check if this browser supports channel messaging

if (window.MessageChannel) {

/* Use channel messaging in this browser */


You can find a full list of new functionality available to developers in the IE10 developer guide here. We look forward to continuing to engage the community and listening to your feedback.

Dean Hachamovitch

P.S. We encourage developers to try out the improved innerHTML support in this second Platform Preview of IE10.

Comments (76)

  1. Blake says:

    Yay! so cool to see the progress.

  2. cool_scientist_273 says:

    Awesome work guys…. i hope W8 comes out at the earliest .. Though people  generally prefer chrome they're willing to listen to my why IE9 talks as it has substance…. but speed and usability hav to be enhanced.. Keep at it guys and  may u come out on top :)

  3. Scott Cranfill says:

    For the love of all that is holy, when are you going to implement text-shadow? At least freaking COMMENT on a timetable for doing so.

  4. David says:

    I and many others hope that text-shadow will finally come to IE10 like in the other browsers :)

  5. rosieks says:

    Please improve DevToolbar experience.

    It will be nice to have margin/border/padding highlighting like in Firebug, live DOM refresh in HTML tab and 0.availability of Cookies tab.

  6. RocketMan says:

    Can the text-rendering engine in IE be so poor that text-shadows are beyond its capabilities?  I mean this is about the most basic-of-basic CSS3 features that every browser EXCEPT IE has supported for ages.

  7. Palermo4 says:

    From the HTML5 Web Camps please access starter files here

  8. text-shadow says:

    IE doesn't like me, why oh why can't Microsoft and I be friends :(

  9. James Gentile says:

    When I minimize IE (9 or 10 previews), and do some work, then go back to IE, page scrolling by holding the scroll bar is really slow (happens for sure on , not sure if happens on all other sites or just some though.)  Other browsers don't have this problem..

  10. Arieta says:

    Nice. With columns support, text-shadow is the most important missing thing. Then you guys can work on a GOOD, customizable UI. Also, user features. IE already allows sites to be viewed with a custom CSS (can do this since at least IE5.5, but probably way longer), you could easily expand this to set up per-site rules – and add not just css but javascript support too, thus adding support for two of the most popular plugins on any other browser.

  11. duri says:

    Good job guys. I wonder why IE10 PP2 doesn't support CSS3 animations and transitions, which were seen working in Internet Explorer from leaked Windows 8 builds.

  12. Jack says:

    It's hilarious how overt this article is about "yeah, well, Chrome and Firefox don't do this. :smug:" How about text-shadow? CSS animations? 2D transitions? History push? Web sockets? Border-image?

    It's awesome that IE10 is making big strides, and it's great to talk about what's new – but don't be so snide about the few things it does better, when it's still missing so much.

  13. Prior Semblance says:

    Sounds awesome, was happily surprised to see HTML5 forms mentioned =]  Downloading now =D

  14. Björn says:

    Wohooo, floats have never felt that great since IE7 fixed the quirks of its predecessors.

  15. Manufacturer says:

    Nice work you guys did there.

  16. blepore says:

    VERY happy to see HTML5 forms and the FileReader supported. Now it just needs sendAsBinary on XMLHttpRequest (like Mozilla) or BlobBuilder/WebKitBlobBuilder+ArrayBuffer+Uint8Array and my 'resize JPG/PNG files before upload' tool will work in IE10 like it does in Chrome and Firefox. At the very least it won't need to run Flash to upload multiple files. :)

    I am absolutely thrilled at the progress IE is making. But seriously, what is up with the lack of text-shadow? The lack of it from IE9 was a major head scratcher. What the heck?

  17. Stilgar says:

    HTML5 Forms finally! The most useful thing for real world developers in HTML5. All the shiny demo canvas/video/etc. bullshit is not important.

    I actually wrote an angry comment about the lack of HTML5 forms after watching the video that did not mention the new input types but for some reason it was not posted :)

  18. Miguel WebDeveloper says:

    Cool feature for the lights  :)

    Is message channel w3c standard??

  19. Charles says:


  20. Adrian Bateman [MSFT] says:

    @Miguel – MessageChannel is defined in the W3C Web Messaging spec here:…/postmsg

  21. zilch says:

    I've just seen floats on steroids. Great job, MS and Adobe!

  22. Matt Wood says:

    You are very keen to promote your own in-house benchmarks, and even the benchmarks of others when it suits you (e.g. Sunspider). But why have I not once seen Google's V8 benchmark mentioned on your site, despite it being considered an industry-standard benchmark for JavaScript performance?

    Is it because IE is still rubbish at it?

  23. Congratulations for the fast progress and the many improvements!

    I am glad to see HTML5 Forms starting to be implemented, and I look forward to some more widgets / GUI for them :-)

  24. Noah says:

    The HowStuffWorks demo looks correct on Chrome 14 (dev channel). Why are you comparing a platform preview (alpha?) of IE 10 against a beta of Chrome?

  25. Firefox 7 says:

    HowStuffWorks renders correctly in Firefox 7.0, more like your demo is EPIC FAIL, Gavin.

    But nice try with the lies.

  26. For The Sake of All that is Sacred says:

    Please just stop making browsers…

  27. evil says:

    Will it be another m$ non-standard compliant adoption of HTML5 like IE6 crap or never implemented in msoffice ISO(msoffice supports pre-ISO format) OfficeOpenXML? I am not webdeveloper and didnt wanted to be offensive, but theres no comments about that and W3C HTML5 validator is not ready yet, but its hard to believe that microsoft will iplement really some real standard(but if so, then it would be nice surprise).

  28. hAl says:

    Excellent Javascript standards conformance on the IE10 preview

    IE10 preview scores only 7 fails on the 10935 test in the official Ecmascript standards conformance test at (v0.7.5)

  29. Fontless says:

    Will it be compatible with Helvetica font?  IE9 crashes on any site uses Helvetica, if you have the wrong version of Helvetica installed on your computer.

  30. mt says:

    The comments from "Noah" down till "evil" are excellent points.

  31. David Björklund says:

    95 points on acid 3. Impressive!

  32. Adam says:

    HTML5 Forms!!  Thank you so much.

  33. Marco Aurélio says:

    Nice work on implementing WebWorkers.

    Are text-shadows implemented yet?

  34. c69 says:

    o, thanx guys! positioned floats alone are the reason to see this preview.

  35. Tirta says:

    Cool. Look forward for the final version. I Especially like the GPU and javascript offload to another thread.

  36. Bara says:

    So uh… no text-shadow still?

    Why all this emphasis on baking in new stuff that other browsers are only just starting to add, when you still haven't finished adding stuff that other browsers have had for years?

  37. Roman says:

    Is it possible to announce a roadmap for planned features? I'm sure, somewhere in depths of your dev team there is a tracker list of features to implement. Why don't you share it? This will drop the inevitable questions "When is ____ going to be implemented?"

  38. g.t. says:

    No spell check?, it is ok, back to Google Chrome :-)

  39. EVS says:

    For the love of web devs everywhere… just implement Webkit and be done with it!!!

  40. TheGood says:

    What's with the speed (or lack of) in IE10PP2? I mean on my i7 950 IE9 is 17.4x FASTER than PP2!

  41. Miles says:

    Why is IE still around? Oh awesome much better frame rate! </sarcasm> Why don't you (IE) focus on how to make developer's lives easier. Play nice Microsoft, be better.

  42. webkit says:

    webkit! webkit! webkit!

  43. vantech says:

    This is completely irrelevant while you insist on freezing the web in the last century for XP users. If you're really serious, make a standalone version that uses the same rendering. These are features that DO work on decent browsers anyway, it's thanks to your lock-down that developers can't implement them.

  44. Senthilkumar Peelikkampatti says:

    This is really good news, MS finally on top gear after loosing poll position. Though it is first from last but I hope nothing lost if they improve and good to see that happening. Congrats. Still I need silverlight or flash or addons to run websocket. I hope this IE10 dishout websocket.

  45. about:blank says:

    IE10? IE will become irrelevant in the next 5 years as market share continually falls. Next time build a browser for all Windows customers including XP and Vista. Otherwise, good job.

  46. jayp says:

    Great stuff, web workers are particularly nice to see.

    Not entirely sure why so many people keep banging on about text-shadow – I haven't seen any use of it that actually looks good, as yet.

  47. RP says:

    Great to see progress on HTML5 Forms – thank you

  48. Mr.03 says:

    For all the dumbasses saying "webkit", competition is always good. Look what happened with IE when it had no competition and look at it now.

  49. Esben says:

    Great job, looking forward to the release of IE10 :-) And for all the people shouting for WebKit, why do you want to use a slower browser? IE9/IE10 is much faster when it comes to hardware accelerating.

  50. Jon says:

    A lot of fantastic additions here, good work! Bit confused by what you mean by 'site ready' though? I mean, has float positioning even been accepted as a CSS3 module by the W3C working group yet? Seems a little premature to be saying it's non-experimental.

  51. Richard says:

    Please include a way to delete DOM Storage items in the Delete Browsing History dialog. This is really important for the user's privacy.

  52. Björn says:

    I wonder how the "Positioned Floats" (strange name BTW) react to scrolling. Could you maybe extend the demo for that?

  53. Zkal says:

    @g.t.: Spell check is not part of the rendering engine so no, it's not in a preview that's only for that. If they do include it, it will be in the beta or Release Candidate for the first time.

  54. Steve says:

    FormData doesn't seem to be implemented or enabled? Please confirm!

  55. g.t. says:

    @Zkal: spell check in the beta release? are you sure? which beta release? IE 2025? or IE 2030?

  56. Adrian Bateman [MSFT] says:

    @Richard – Because DOM Storage is similar to cookies, Delete Browsing History removes this data when the Cookies check box is selected. See…/cc197062(VS.85).aspx

  57. Alex says:

    Why don't you put the IE9 interface on the Platform Previews? It would make them useable, and you could include any interface changes at the Beta stage.

  58. petmal says:


    I would love to watch those HTML5 videos you post in full screen. Don't tell me it is that difficult to implement.


  59. Zkal says:

    @g.t.: Do note how I said "If they do include it". We will not find out if it is included or not until beta is out. Before that, it's best to wait since Platform Previews aren't meant for UI features like those.

  60. @Alex says:

    If you want a Beta, wait for Beta.  Preview is designed for a different purpose.…/about-the-platform-preview.aspx

  61. Checked Firefox 7? says:

    Can it beat Firefox 7? No way!…/177360802319901

  62. Alec says:

    Years later and we're still waiting for IE to support text-shadow…

  63. Evil E. says:

    How about adding support for .apng (animated PNG :…/APNG) images in IE10 ???

  64. Aethec says:

    @"Checked Firefox 7?"

    And…that Facebook group composed of FF fanboys proves what?

  65. Ardentra says:

    +1 for Text-Shadow

    There are real world uses for this and I have posted this as a request on Connect for every IE9PP and IE10PP. Awesome work overall.  Spell check and border-image would also be pretty sweet. Text-Shadow should be a no-brainer though.

    For everyone wanting text-shadow open a bug up in connect and log the bug again.

  66. Dave Hodder says:

    I've been exploring the initial HTML5 forms support, and have to say I'm very impressed.  There's more there than the current developer docs suggest (e.g. datalist support).  Congratulations to the IE team!

  67. Gérard Talbot says:

    @Dean Hachamovitch [MSFT]

    > we have posted over 270 new tests to the IE Test Center and submitted them to the standards bodies.

    Some of those Microsoft tests have been rejected but they are still listed (with results for other browsers) at IE Test Center. Why?

    This IE blog software is buggy and dysfunctional.

  68. Gérard Talbot says:

    @Dean Hachamovitch [MSFT]

    > we have posted over 270 new tests to the IE Test Center and submitted them to the standards bodies.

    Some of those Microsoft tests are invalid HTML5 but they are still listed (with results for other browsers) at IE Test Center. Why?

    This IE blog software makes it impossible to provide links in a useful, relevant post.

    Gérard Talbot

  69. Gérard Talbot says:

    @Dean Hachamovitch [MSFT]

    Image element with border in % : invalid XHTML5 testcase

    Object element with border in % :  invalid XHTML5 testcase

    Object element with border in % : invalid XHTML5 testcase

    Impossible to paste links in this blog!

    Dean Hachamovitch, you have the power to tell someone working at Microsoft to fix this IE blog software.

    Gérard Talbot

  70. Gérard Talbot says:

    @Dean Hachamovitch [MSFT]

    <img> element does not have a border attribute in HTML5:…/embedded-content-1.html

    <object> element does not have a border attribute in HTML5:…/the-iframe-element.html

    Gérard Talbot

  71. @Gérard says:

    Gérard, please. We know you're French. You can take a day off.

  72. sanatgersappa says:

    Any plans to support window.applicationCache and offline apps?

  73. Chaz says:

    Spell check please. From an end user's perspective it is the biggest feature gap by a country mile and is the only reason why I still use Chrome now IE9 has closed the speed gap

  74. You are making great work in IE10! Awesome! But we expecting steps forward in HTML5 Web SQL Database feature. It's a important feature that's can empowering HTML5 apps. We all are waiting this feature.

  75. Andrey says:

    File API works great! Please, add FormData API too :)

  76. bella says:

    i have been using ie for 8 years .i only know ie before i use other browsers .chrome and firefox don't fit to me .yeah, they are fast, special and  own lots of big fans .but they also have a lot of bugs  .i'm using avant browser .at first,i don’t like it .no beautiful skins, no add-ons. Now, I love it so much , for its autofill, online storage, backup/restore files, downloader…and so on