Is IE9 a modern browser?

Let's compare IE9 to Firefox 4

HTML5 test

IE9: 130

Firefox 4: 255

Firefox 3.5 (two years ago): 142

source

In 2011, IE9 now supports Canvas, Video, Geolocation and SVG. Firefox came with Canvas and SVG 5 years ago, Video and Geolocation 2 years ago.

Platform supported

IE9: Windows Vista/7.

Firefox 4: Windows Vista/7, Windows XP, GNU/Linux, Mac OS, Android.

HTML5 compatibility

IE9: 54%

Firefox 4: 88%

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CSS3 compatibility

IE9: 74%

Firefox 4: 87%

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JS API compatibility

IE9: 48%

Firefox 4: 90%

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All Web Standards Compatibility

IE9: 61%

Firefox 4: 87%

Firefox 3.6 (one year ago): 65%

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Hardware Acceleration

Firefox 4 = IE9

On Windows Vista/7, Firefox 4 supports Full Hardware Acceleration, as much as IE9. No more, no less.

Firefox 4 also supports Hardware Acceleration on Mac and Windows XP (Compositing Acceleration) and Linux (Content Acceleration).

on compatible hardware

source

What's missing in IE9?

compared to Firefox 4

WebGL, MathML, Web Workers, HTML5 Forms, JavaScript Strict Mode, CSS3 Transitions, SVG Filters, foreignObject, text-shadow, SMIL animations, File API, History API, XMLHttpRequest Level 2, FormData, CSS3 Gradients, border-image, columns, classList API, Drag'n Drop from Desktop, Flexible Box Model, App Cache (offline), IndexedDB, ...

What's missing in Firefox4?

compared to IE9

Text-overflow

source