Html5 Plugin For Firefox
Is there a plugin for Firefox to validate HTML 5?
I've always used this, but if my webpage has a <!DOCTYPE HTML> doctype it complains about it not having a doctype at all.
I specifically would like one similar to the one I linked, where the verification happens on your computer and instantaneous and automatic, without needing to send any data to a third-party server and then wait for a reply.
4 Answers
This is the best one I found so far:
https://github.com/rogerjohansson/html5validator (see Downloads for an xpi)
You should not use the validator.nu online service with it, since it causes a DoS attack on the online service, and you will probably be banned from using the service as a countermeasure (see https://github.com/rogerjohansson/html5validator/issues/6). 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 this. You would then have a locally-running validator and can even check sites without an Internet connection by filling in http://localhost:8888/ (the default address of the local validator instance) into the Validator URL of the addon.
To give credits: I have the information above from Validating HTML5 with validator.nu and the HTML5Validator Extension for Firefox.
On the Web Developer add-on, https://addons.mozilla.org/en-US/firefox/addon/60, if you use 'Tools' > 'Display Page Validation' it will show a bar at the top validating the page source code. This is done via the W3C validator, but without you having to navigate there.
It is a shame the HTML Validator has no plans as of yet to incorporate HTML5 until at least version 0.9.
This says it will do it: https://addons.mozilla.org/en-US/firefox/addon/2318 and I found this also: http://html5.validator.nu/
You can validate HTML5 at the following site:
Make sure on the options that you select the HTML5 document type.
Not the answer you're looking for? Browse other questions tagged firefoxbrowser-addonshtml5 or ask your own question.
I just wrote a tutorial on disabling auto-playing Flash and HTML5 videos in Firefox and Chrome in which I mentioned Firefox's media.autoplay.enabled preference to disable some -- but not all -- HTML5 videos from playing automatically.
The reason why this works only on some sites but not on others is because of how sites implement the player and play() calls. Sites may call play() directly without using autoplay, and if that is the case, they are not blocked by Firefox's current implementation of the feature as it only blocks videos if autoplay is explicitly used.
This is for instance the case on YouTube which you can test easily by setting the preference to false in Firefox before you play a video on YouTube afterwards. You will notice that the video plays automatically when you open the site.
At least, that is the case if you run a version of the browser prior to 41. If you run the latest Nightly build of the browser, you will notice that Mozilla fixed the issue.
Setting the preference to false and visiting YouTube afterwards will stop all videos from playing automatically on the site.
The bug listing, opened back in 2011 had to be reopened multiple times as Mozilla, for varying reasons, did not implement the change in the browser.
Work on it began just a couple of days ago and the final patch that resolves the issue landed for Firefox 41 versions quickly afterwards.
Firefox 41 is currently available in the Nightly channel. This means that Stable users will have to wait a couple of months before it lands in their version of the browser (it takes six weeks to move to a new version with the next update to version 39 being released on June 30, 2015).
Mozilla aims to release Firefox 41 on September 22 to the stable channel of the web browser.
Instructions to enable the blocking of HTML5 video in Firefox
Do the following to block HTML5 video autoplay in the browser:
- Type about:config in the browser's address bar and hit enter.
- Confirm that you will be careful if the notification comes up.
- Use the search at the top to find the preference media.autoplay.enabled.
- Double-click on it.
Doing so once sets the preference to false which turns autoplay off for HTML elements in Firefox. You can reverse that at any time by double-clicking again, or by right-clicking on the preference and selecting the reset option from the context menu.