While this is definitely not an answer to the question originally asked, I still think it's worth mentioning: HTML5 video, while ideologically better, may result in utterly terrible performance. When using youtube with the HTML5 player, I consistently see the CPU hit 100% no matter which machine I use, and stuttering is frequent. This indicates that there's a whole lot of software-decoding going on. When using the Adobe Flash Player w/HW accelleration[1], I'm getting the expected 10-20% CPU consumption while playing video. If a Core i7 with 12GBs of RAM cannot reliably play back HTML5 vide – May 3 '14 at 11:23. Firefox 33 and beyond Mozilla added support for OpenH264 as a plugin in. To enable this plugin Firefox will now automatically download a binary from the the first time you start the program.
Check out the 10 best HTML5 audio player plugins for WordPress and see how they can assist you in integrating a unique and feature-rich media player into your WordPress-based website or blog! I've read about how HTML5 will change the way I use the web, but it seems like the biggest example of HTML5 in action is on sites like YouTube—which don't support my favorite browser, Firefox. What's the deal? Advertisement Firefox and Safari partially support it, Google's Wave and Chrome projects.
That sounds great, doesn't it? Wait that was a pun. While this is indeed a very convenient solution it should also raise privacy and security concerns when software automatically downloads binaries from sites affiliated with Cisco Systems or other companies, no matter how transparent the process and license agreement is. Not directly related but if you prefer to automatically delete cookies when Firefox gets closed and can't find the right cookie to keep for persistent HTML5 playback then I suggest to install.
Tests with 14.04.2 and 15.04 VMs My guess was that only installing an H.264 decoder binary wouldn't be enough, so I set up 2 new virtual machines: • Ubuntu 14.04.2 with restricted addons installed during installation • Ubuntu 15.04 without restricted addons installed during installation After the installation of both VMs was completed I booted the systems, updated them again, installed VM guest additions, started Firefox for the first time and rebooted for the actual testing. Since YouTube also offers their open sourced formats and I wanted to avoid going into to much detail about test methods I needed to use another HTML5 capable site to test proprietary H.264 playback support. I chose Vimeo, because they say they and they don't to support WebM, which I consider not to be a good thing. Whenever I made some changes in the test, like installing a package or enabling/disabling something in Firefox I closed and launched Firefox again. 14.04.2 with restricted addons As you can see in this screenshot only the OpenH264 plugin is enabled in Firefox, all the necessary GStreamer packages in different versions are preinstalled and the video plays as expected. 15.04 without restricted addons As you can see in this screenshot the OpenH264 plugin is enabled, there is no Flash plugin, a few GStreamer packages in different versions are preinstalled but the video does not play! Instead the site immediately tells us that the video can't be played.
• It is perfect for professionals. 
• It is capable of using the 3D graphics.
• AAC is missing! – To put an explanation simple, there is a file on the server that is fed into our browser. If you look for it using the inspector from the context menu in Firefox, you will find an MP4 with AAC-encoded audio. The error message could be more clear but it makes sense since we don't have a decoder for AAC currently installed.
• Update: Looking again into this issue with Firefox 41, I found that OpenH264 seems to be disabled in about:config through: media.fragmented-mp4.exposed;false media.fragmented-mp4.gmp.enabled;false Setting these to true had no effect. Further settings I tried: • media.audio_data.enabled;true no effect. • media.mediasource.enabled;true Vimeo didn't use MSE before, enabling these and related settings had no effect. • media.fragmented-mp4.use-blank-decoder;true result: a solid green canvas and a constant sine wave audio signal. 15.04 with restricted addons A smart approach would have been to install gstreamer1.0-plugins-bad-faad, but this doesn't make the particular error message on Vimeo go way, so let's install all the restricted addons. As expected, everything works if you install the restricted addons package, but you may want to set the Flash plugin to something else than enabled in Firefox to be sure to use HTML5 video.
Analysis or just make it break Apparently gstreamer1.0-libav is the only package you need to remove to get the error message back. So it was using libav's AAC decoder? I didn't dig deeper to find proof for that nor did I look for which decoder will be preferred (e.g. If OpenH264 is of any use currently on Linux) or if Vimeo throws this error message due to some other dependency not being met despite H.264 and AAC decoders being installed. Summary and outlook To sum it up, playback of current mainstream content does not only require an H.264 decoder but also an AAC decoder and H.265 is already preparing to replace the older one. Also I don't see the corresponding to be changed towards recommending a more open source friendly audio codec in the foreseeable future.
Seriously, push for WebM! You get VP8 + Vorbis as the H.264/AVC contender and VP9 + Opus as the H.265/HEVC contender.
It’s no secret that Steve Jobs hated Flash; he was singlehandedly responsible for its downfall. His reasons, all valid, can be read in. On the web, yes, Flash lost. The web was no longer filled with ugly and slow splashes of Flash based websites. The web is a lot prettier than it used to be. Shameless plug: Check out. It’s what we call “beautifully informative”.
And not a single line of Flash code was used in its making. Flash is still prevalent when it comes to videos though. While front end languages were ready to take over the interactive elements of the website, HTML and video playback still weren’t best pals. HTML5 mug by slavik_V on Flickr. It’s much better now, with the HTML5 spec being finalized and browser support at a plateau.
What I’m getting at is that while many websites still like to squeeze Flash videos down the internet cables, they really don’t have to. And though YouTube is moving a lot of its videos to the HTML5 format, we’re clearly not all the way there. In this guide, we’ll focus on how to force HTML5 videos on websites like YouTube and Vimeo (as much as we can). Why Would You Want To Do This?
We know Flash on the whole is bad, but why would you want to switch from Flash video to HTML5? • HTML5 videos are less resource intensive. They load up faster. • They don’t take nearly as much power to run, which means your laptop’s. • To me, and I have no scientific way of proving this, HTML5 videos look crisper played at 720p resolution on my Retina MacBook Pro.
And of course, there are downsides as well. For the most part, HTML5 videos don’t support 1080p resolution. If you’re addicted to, this solution might not be for you. Again, in my opinion, the 720p HTML5 playback is really nice. YouTube has its own HTML5 videos page: YouTube’s own just states that whenever possible, it will load HTML5 videos but it gives no details about which ones.
Chrome Extensions. HTML5ify will block Flash content wherever it can and replace it with HTML5. Besides YouTube, it will force HTML5 players in Vimeo as well (if you’ve viewed more than a couple of Vimeo videos, you know the built-in player is unnecessarily complicated). HTML5 video for YouTube does pretty much the same thing as HTML5ify, except it adds a strip of UI below every video.
HTML5 support for high definition videos is still tricky. 
So you might have to make do with 720p resolution. The dropdown menu below the video player gives you options for selecting the quality. Firefox Add-ons YouTube ALL HTML5 adds a button that switches the current video to HTML5 format. YouTube HTML5 Video is a simple add-on that inserts “&html5=1” at the end of each YouTube URL forcing the video to load in HTML5.
If you’ve got 100% confidence in HTML5 videos and don’t want to click a button every time, use this add-on to basically automate the process. YouTube HTML5 Player is much like YouTube ALL HTML5. It presents you with a button that when pressed, switches from Flash to HTML5 video.
Flash Or HTML5? It’s your turn now. Flash or HTML5 – which is your preferred online video playback format? Let us know in the comments below. Last updated on 8 Feb, 2018.
This is the best one I found so far: (see Downloads for an xpi) You should not use the validator.nu online service with it, since it causes a attack on the online service, and you will probably be banned from using the service as a countermeasure (see ). The cool thing is, it does not send the URL to the validator, but the HTML data directly; this means that local sites or password-protected sites can also be checked. Validation can be turned on automatically, by a domain-whitelist or by clicking the validator item.
You can and should up your own validator.nu-instance (at least on Linux and Mac OS X) - see. You would then have a locally-running validator and can even check sites without an Internet connection by filling in (the default address of the local validator instance) into the Validator URL of the addon.
To give credits: I have the information above from.