We last compared these numbers a few months ago and while HTML5 compatibility has greatly increased from IE9 to IE10, it’s still not as robust as Android (ICS), iOS6 or BlackBerry 10.
The current build of Windows Phone 8 scored 319 (+ 6 bonus) on the HTML5 Test with iOS6 (via the iPhone 5) coming in at 360 (+9 Bonus). Of course all of that is ironically trumped by RIMs in-gestation BlackBerry 10, which has a super high score of 447 (+10 bonus) and while that is high, 3rd party browser Dolphin for Android (currently in beta) gets 450 (+3 bonus).
Some of the latest features in IE10
- IE10 for Windows Phone 8 - 319 (+ 6)
- iPhone 5 - 360 (+9)
- BB10 (beta) – 447 (+10)
- Dolphin (beta, Android) – 450 (+3)
Does HTML5 mean that much? Yes and no. For one, the HTML5 feature list is in flux, although the test takes that into consideration when breaking down scores. In short, yes, having a higher score is better as it means when it comes to forms, data entry, rendering tables, etc. the more compatible the browser, the more accurate it will look. Does it mean that we will notice the difference? Maybe not but we wouldn’t lie in saying we wish Windows Phone 8 scored a little higher (even if it nearly tripled its IE9 score of 121).
Of course there are other browser benchmarks to consider, including speed and how the OS itself handles things. For that, we’ll have to wait a little longer. One thing though is for certain, the competition is not resting on its laurels when it comes to mobile browsers these days. And regardless of HTML5 tests, we're confident that IE10 on Windows Phone 8 will be a great improvement over its predecessor.
Edit: A lot of people seem to be suggesting that the areas where IE10 on Windows Phone 8 is lagging are non-important, "experimental" features. This is quite far from the truth though. Most of the features missing compared to other platforms, including iOS6 are in fact 'Official HTML5 specifications'. Only 1 was experimental: Web Audio API.
Related and more information: iOS6 Safari currently beats out Windows Phone 8 for HTML5 features