Here are the latest features in Firefox for developers, as part of our Bleeding Edge series, and most examples only work in Firefox Nightly (and could be subject to change).

<video>: support for custom playbackRate

Setting video.playbackRate changes the “video speed”. 1.0 is regular speed, 2.0 is 2 times faster. From the MDN documentation on HTMLMediaElement:

The default playback rate for the media. 1.0 is “normal speed,” values lower than 1.0 make the media play slower than normal, higher values make it play faster.

Example:

fast foward

Interactive demo:

video playbackRate demo

<a> “download” attribute

From Downloading resources in the Living standard at Whatwg.org:

In some cases, resources are intended for later use rather than immediate viewing. To indicate that a resource is intended to be downloaded for use later, rather than immediately used, the download attribute can be specified on the a or area element that creates the hyperlink to that resource.

This attribute is particularly useful with blobs. With Blobs, You can create files in JavaScript. A binary blob can be an image built in a canvas element for example. Linking binary blobs to a <a> element (with a URL constructor) and marking this <a> element as downloadable with this new attribute, the user will be able to save the blob as a file on his hard-drive.

Example from Tom Schuster’s blog post about his work on the HTML5 download attribute: ]

var blob = new Blob(["Hello World"]);
var a = document.createElement("a");
a.href = window.URL.createObjectURL(blob);
a.download = "hello-world.txt";
a.textContent = "Download Hello World!";

It has also been covered on HTML5Rocks in Downloading resources in HTML5.