Question

What are the features of HTML5 that can be reliably used today?

Microsoft has some cool HTML5 demos, but what part of it is classic EEE and what is them catching up?

Example of useful feature I found on SO: pushState.

Please give more thought than a page with comprehensive lists of tags and attributes of HTML5.
@Jan Zyka’s http://slides.html5rocks.com answer is a great example. (Thank you!)

What are you actually using in production code today?

Answer 1

There is a site called When can I use… which lists a variety of HTML5, CSS3, and other modern web standards, and gives an indication of which browser versions support it.

Whether or not you can use a feature depends a lot on who your users are. If you’re targeting cutting-edge web developers, then you can likely rely on them having much later versions of browsers than if you’re targeting corporate accounting. So, you will need to decide which browser versions you must support, and do appropriate progressive enhancement or fallback to support older browsers while introducing newer features that they don’t support.

Some HTML5, CSS3, and other features can be used in older browsers using “polyfills,” which are implementations of missing features using JavaScript, Flash, proprietary features, and the like. For instance, you can use <canvas> elements in older versions of Internet Explorer by using ExplorerCanvas, which implements the HTML5 <canvas> element using JavaScript and Microsoft’s proprietary VML. The “When can I use…” site lists polyfills for many features, so check the polyfills checkbox if you’re willing to use polyfills.