HTML5 Articles

Sort by:


  1. New features for HTML5 video playback in Firefox

    As explained in this blog post by Jared Wein of the Firefox team there are quite a few new features in Firefox when it comes to playing HTML5 video. As an Aurora user, I am most excited about the option to go full-screen, the ability to overlay video statistics and to save a snapshot of the current frame as a JPG. You can see me talking about and showing them in this short video:

    Firefox has a few features up its sleeve when it comes to HTML5 video playback you might not be aware of:

    • Firefox‘s seeking is now accurate to millisecondsmicroseconds, there is visual feedback when the video has stalled and clicking the whole video pauses and plays it
    • Firefox Beta has specialised controls when you watch video on small devices and watching HTML5 video shows a pleasing background rather than a brutal grey
    • Firefox Aurora has fullscreen, statistics overlay, saving of snapshots and controls appearing when the video ended
    • Firefox Nightly has a full-screen button, fading video controls after 2 seconds of non-interaction, no loading throbber on audio, error reporting when a video could not be loaded on the video, loop attribute support, and resizing of videos larger than the browser window when you watch them directly

    Planned features for Firefox are an overlay play button like YouTube when the video is not set to autoplay and turning off screensavers during fullscreen playback.

    Check out Jared’s post for more information.

  2. Moving browsers and the web forward (video)

    A few days ago I was asked to deliver the first talk of the amazing Beyond Tellerand conference in Dusseldorf, Germany. The talk Breaking the barriers – moving browsers and the web forward introduced a lot of new ideas and technologies that are worked on my Mozilla and others to make the web of the future better.

    Here is the video of the presentation with jump points and links to more information. If you want to see the slides of the talk, they are available here and there is also an audio recording on

    Breaking the barriers – moving browsers and the web forward from marc thiele on Vimeo.

    Here’s what is covered in the talk:

    1. Modern web technologies of HTML5 and friends that can be used right now (with 64 myself as a demo) [03:50 - 07:19]
      • Rich HTML semantics (HTML5)
      • Self-validating forms (HTML5)
      • Richer form controls with fallbacks (HTML5)
      • Canvas for painting in the browser (HTML5)
      • CSS gradients, multiple backgrounds, animation and transition
      • CSS 3D transforms
      • Local storage and offline storage
      • SVG for scalable and interactive graphics
      • RequestAnimationFrame for secure animation
      • History API
      • WebGL
    2. Taking on challenges – we need you to show the world that web technology is good enough to do jobs that in the past were only possible with native or server-side code (with Joe Lambert’s image unshredder as the example) [07:20 - 08:04]
    3. Breaking the browser mould – showing that the browser interfaces can be manipulated with HTML and JS (with browser menus, context menus and the Fullscreen API as examples) [08:05 - 10:54]
    4. Developing with the web – developer tools in browsers and done in client side technologies (with Hackasaurus, Cloud 9 IDE, Firefox Scratchpad, Firefox Style Editor, Parse error display in view-source and Tilt as examples) [10:55 - 17:24]
    5. Online identity and issues with current login systems (with BrowserID as a solution to a lot of the problems we have right now) [17:25 - 29:35]
    6. Apps, the shortcomings and myths of native apps and the opportunity to build hybrid apps with web technologies (with Open Web Apps and Web Intents as examples) [29:36 - 37:34]
    7. Moving web technologies into the mobile space (with Are we mobile yet? and Boot to Gecko as demos) [37:35 - 40:11]
    8. How can you help? [40:12 - 42:33]
  3. Luke Crouch on: HTML5 – code for all the platforms

    Back in October, Luke Crouch, one of the web developers working on the Mozilla Developer Network went to Techfest in Tulsa, Oklahoma to tell people all about HTML5. You can see his slides with his voiceover at

    Luke Crouch: Code for all the platforms

    Luke gave an overview on the history of HTML5 vs. XHTML and the approaches of the W3C and the WHATWG. He explains how standards are produced and how this can be daunting. He then shows how “shipping code wins” and showcases lots of examples of new technology in action.

    He concludes with a nice comparison on how much simpler it is to build rich form interfaces with HTML5 and polyfills than with native code for various platforms.

    All in all a presentation very worth while from someone who is in the trenches and who is not afraid to use new technology and wait for the market to catch up.

  4. HTML5 context menus in Firefox (Screencast and Code)

    You may not know it, but the HTML5 specifications go beyond what we put in the pages and also define how parts of the browser should become available to developers with HTML, CSS and JavaScript. One of these parts of the specs are context menus, or “right click menus”. Using HTML5 and a menu element you can add new options to these without having to write a browser add-on. In Firefox 8 (the current one) we have support for those. See the following screencast for a context menu demo.

    The image example is pretty simple and was actually written by Paul Rouget as a demo in the original Firefox bug request. The main core is the HTML of it:

    <section id="noninteractive" contextmenu="imagemenu">
      <img src="html5.png" alt="HTML5" id="menudemo">
        <menu type="context" id="imagemenu">
          <menuitem label="rotate" onclick="rotate()"
          <menuitem label="resize" onclick="resize()"
          <menu label="share">
            <menuitem label="twitter" onclick="alert('not yet')"></menuitem>
            <menuitem label="facebook" onclick="alert('not yet')"></menuitem>

    As you can see you link the menu element to an element via its ID. The contextmenu attribute then points to this one. Each menu can have several menuitems. Each of those gets a textual label and a possible icon. You can also nest menu elements to create multiple layer menus. Here, we add inline onclick handlers to point to different JavaScript functions to call when the menu item gets activated. The resulting context menu looks like this:

    image with a context menu

    The functionality is simple, all the rotate() and resize() functions do is add class names to the image using querySelector and classList:

    function rotate() {
    function resize() {   

    The real effect is in CSS transforms and transitions. As the image has an ID of menudemo here is what is needed in CSS to rotate and resize:

    #menudemo { 
      -moz-transition: 0.2s; 
    #menudemo.rotate { 
      -moz-transform: rotate(90deg); 
    #menudemo.resize { 
      -moz-transform: scale(0.7); 
    #menudemo.resize.rotate { 
      -moz-transform: scale(0.7) rotate(90deg); 

    Notice that in a real product we should of course add the other browser prefixes and go prefix-less but as the functionality now only works in Firefox, this is enough for this demo.

    Detecting support and visual hinting

    Now, as this is extending the normal user offerings in the browser we need to make it obvious that there is a right-click menu available. In CSS3, there is a context-menu cursor available to us. When context menus are available, this should be shown:

    .contextmenu #menudemo, .contextmenu .demo {
      cursor: context-menu;

    We test the browser for support by checking for contextmenu on the body element and for HTMLMenuItemElement in the window (this has been added as a pull request to Modernizr, too).

    if ('contextMenu' in document.body && 'HTMLMenuItemElement' in window) {
    } else {

    Wouldn’t HTMLMenuItemElement be enough? Yes, but a real context menu should only offer functionality when it is sensible, and that is where contextMenu comes in.

    Turning menuitems on and off depending on functionality

    As a slightly more complex example, let’s add a “count words” functionality to the document. For this, we generate a counter element that will become a tooltip when the words were counted:

    var counter = document.createElement('span'); = 'counter';
    counter.className = 'hide';
    counter.addEventListener('click', function(ev){
      this.className = 'hide';

    This one is hidden by default and becomes visible when the hide class is removed. To make it smooth, we use a transition:

      position: absolute;
      background: rgba(0,0,0,0.7);
      padding:.5em 1em;
      color: #fff;
      border-radius: 5px;
      -moz-transition: opacity 0.4s;
      opacity: 0;

    We start with two sections with context menus:

    <section id="noninteractive" contextmenu="countmenu">
      <menu type="context" id="countmenu">
          <menuitem class="wordcount" label="count words"></menuitem>
    <section id="interactive" contextmenu="countmenuinteractive">
      <menu type="context" id="countmenuinteractive">
          <menuitem class="wordcount" label="count words"></menuitem>

    We then loop through all the menuitems with the class wordcount and apply the functionality.

    var wordcountmenus = document.querySelectorAll('.wordcount'),
        i = wordcountmenus.length;
    while (i--) {
      wordcountmenus[i].addEventListener('click', function(ev){
        // add functionality 
      }, false);

    We need to find out what has been selected in the page. We do this by using getSelection() and splitting its string version at whitespace. We then show the counter by removing the hide class name.

    var wordcountmenus = document.querySelectorAll('.wordcount'),
        i = wordcountmenus.length;
    while (i--) {
      wordcountmenus[i].addEventListener('click', function(ev){
        var text = document.getSelection(),
            count = text.toString().split(/\s/).length;
        counter.innerHTML = count + ' words';
        counter.className = '';
      }, false);

    You can see this in action in the second context menu demo. Now, the issue with this (as explained in the screencast) is that it always counts the words, regardless of the user having selected some text. What we want is the menu only to be active when there is text selected.

    context menu item available or not available depending on selection

    So in order to make our menu only become available when it makes sense we check if there is a selection in the document. Every context menu fires an event called contextmenu when it opens. So all we need to do is to subscribe to this event.

    When something is selected in the document document.getSelection().isCollapsed is true. Otherwise it is false, so all we need to do is to enable or disable the menu item accordingly:

      'contextmenu', function(ev) {
        this.querySelector('.wordcount').disabled =

    The last thing to solve is the position of the mouse to position the counter element. As the menu selection event doesn’t give us the mouse position we need to add a contextmenu handler to the whole document that positions the counter invisibly behind the menu when it is opened:

      'contextmenu', function(ev) { = ev.pageX + 'px'; = ev.pageY + 'px';
        counter.className = 'hide';

    Further reading and resources

  5. Announcing Firefox Aurora 10

    We’re happy to announce the availability of Aurora 10.
    (Download and Test Aurora 10)

    In additional to the normal improvements that you’ve come to expect like performance, security and bug fixes, Aurora 10 focuses in HTML5 enhancements.

    New additions

    Developer Tools

    Aurora 10 also implements incremental enhancements like IndexedDB setVersion API changes. Ongoing detailed attention to evolving specifications help to keep Firefox at the front of the Web revolution. (Read more about IndexedDB on MDN.)


    • We now fire a “load” event on stylesheet linking when the sheet load finishes or “error” if the load fails.
    • We turn the POSTDATA prompt into an information page (when navigating in session history).
    • We only forward event attributes on body/frameset to the window if we also forward the corresponding on* property.
    • We no longer allow more than one call to when we allow popups.
    • We fixed a bug where a success callback never fired when a position update is triggered after getCurrentPosition().
    • We removed replaceWholeText().
    • We fixed an error with createPattern(zero-size canvas).
    • We now handle putImageData(nonfinite) correctly.
    • We now throw INVALID_STATE_ERR when dispatching uninitialized events.
    • We’ve made Document.documentURI readonly.
    • We fixed document.importNode to comply with optional argument omitted.

    Web workers

    • We now allow data URLs.
    • We implemented event.stopImmediatePropagation in workers.
    • We made XHR2 response/responseType work in Web Workers.


    • We implement the WebGL OES_standard_derivatives extension.
    • We implement minimal-capabilities WebGL mode.


    • The function caller property no longer skips over eval frames.
    • We fixed E4X syntax so that it is not accepted in ES5 strict mode.
    • weakmap.set no longer returns itself instead of undefined.
    • We implemented the battery API.

    Offline: IndexedDB enhancements

    • IndexedDB setVersion API changes
    • Added support for IDBObjectStore/IDBIndex.count
    • Various methods accept both keys and KeyRanges.
    • Added support for IDBCursor.advance.
    • Implemented deleteDatabase.
    • objectStoreNames are no longer updated on closed databases when another connection adds or removes object stores
    • IDBObjectStore.delete and IDBCursor.delete now return undefined.
    • No longer throws an error if there are unknown properties in the options objects to createObjectStore/createIndex.
    • We now the errorCode to “ABORT_ERR” for all pending requests when IDBTransaction.abort() is called.
    • Fixed the sort order for indexes.


    • We have updated the current rule for handling malformed media queries.
    • We now support the HTML5 <bdi> element and CSS property unicode-bidi: isolate.
    • The CSS3 implementation now supports unicode-bidi: plaintext.


    • Implemented Document.mozFullScreenEnabled.
    • Enabled the DOM full-screen API on desktop Firefox by default.