I am the author of the Firefox extension. I have recently rewritten it for Chrome and the new Webextension API of Firefox.
See more info on the extension homepage:
http://users.skynet.be/mgueury/mozilla/index.html
The direct link from the Google Chrome store is this:
https://chrome.google.com/webstore/detail/html-validator/mpbelhhnfhfjnaehkcnnaknldmnocglk
Enjoy,
Answer from mgueury on Stack OverflowI am the author of the Firefox extension. I have recently rewritten it for Chrome and the new Webextension API of Firefox.
See more info on the extension homepage:
http://users.skynet.be/mgueury/mozilla/index.html
The direct link from the Google Chrome store is this:
https://chrome.google.com/webstore/detail/html-validator/mpbelhhnfhfjnaehkcnnaknldmnocglk
Enjoy,
There is a new HTML validator available for Chrome. It uses a JavaScript port of LibTidy and thus validates locally without the need of remote services.
See https://chrome.google.com/webstore/detail/anjdemaoejlpgmnmkijdemoiebcddhkc
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.
I have HTML Validator installed. It does a pretty good job, a simple icon in the toolbar will tell you when something is off:
If you click the icon you get the source code with a list of errors:
I use it to validate pages locally before uploading them.
If you would like to invest some time and disk space the definitive validator is the W3C online validator.
You can however also download a snapshot of the validator and run it yourself offline, you will need an instance of Apache Web server, Perl, some Perl libraries and the validator itself.
This guide explains how to install and run your own validator instance on Windows. For other platforms the installation guide gives details.
All the above is available Free, Gratis and Open Source - you are encouraged to feed back any bugs you spot and you are obliged by the GPL licence to give back any bug fixes and/or enhancements that you might make.
As an example I ran this page through the W3C validator and it came up with the following report:
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.