Big List of HTML Validators

When you’re blogging, most of the time you won’t be editing HTML directly.  But, if your posts start to look strange, there might be invalid HTML behind the scenes. Or, maybe you fat-fingered some custom code and you’re wondering which tag you forgot to close.

Running the code through one of these HTML validators or plugins listed below will help you find the culprit.

html validators, plugins and cleaners

HTML Validators

Modern browsers are built to be forgiving, rendering pages even if they contain a little code that’s invalid. But even if a page looks OK, the structure underneath is what’s important.

Why should you care if you’re just typing your posts in a textbox and not dealing with HTML? Errors hurt your load times. Readers won’t come back if a page loads slowly. If nothing else, you should know what this does to your SEO. Search engine algorithms are more likely to ding pages with “slow” HTML.

That’s why you should seriously consider cleaning up your HTML code, even if you use a blog engine.

Browser Extensions

Browser extensions are a convenient option for HTML validation. These are the ones we think are worth checking out:

Firefox HTML Validator

Mozilla not only makes an awesome web browser, Firefox, but they’re also staunch advocates of the open web and web standards. They prove it with their add-on, appropriately named HTML Validator.

FireFox HTML 5 Editor

This is a separate add-on for Firefox by Eric Vold that handles HTML 5 exclusively. It might seem like a pain just to use a separate plug-in just for HTML 5, but there are enough substantial differences from the old version that it’s justified. The industry is moving toward HTML 5, so it’s worth validating against the new standard.

HTML Validator for Chrome

Chrome is a great browser, and one of the reasons it’s so popular is that there are so many add-ons available for it, just as with Firefox. There are several HTML validators available for Chrome, including one that’s imaginatively titled “HTML Validator.”

Validity for Chrome

Validity is another great free add-on for Chrome that checks HTML. Just click the button in your toolbar and you can validate a web page. You might validate a page on a staging server before you go live or validate someone else’s page and cackle with glee at their errors.

Zappatic for Safari

HTML validation on the Safari browser can be done through Zappatic. Zappatic works by validating HTML code through the W3C and Tidy libraries and integrating the output into the browser. Once a web page is validated, users can see a summary of the number of errors and warnings. Clicking on the notification will bring up a detailed list. HTML5 validation is also supported by Zappatic – but please review the privacy warnings on their website about HTML5.

Online HTML Validators

W3C Validator

W3C Validator screenshot

This is the granddaddy of HTML validators, the World Wide Web Consortium’s (W3) own. You know that your code is valid with this generator, because it’s from the maintainers of the current standards. You can’t get much more authoritative than that. You can paste in either whole pages or short snippets and see if they’re valid.

Free Formatter

Free Formatter is another great free HTML validator. Like the others, it’s dead simple. Just paste your code and click the button, and you see your errors

This validator is Spartan. Just type a URL in the box and it show your errors. You can also upload files or paste in code. There are some options you can change. It supports different schemas, different markups like MathML. It can also show you an outline of your page.


Bing Markup Validator

Microsoft’s Bing search engine is solid if perhaps overlooked. One tool it has is a markup validator.

Aborla Validator

Aborla Validator is a very cool little site. It will not only show you your errors, but will generate a repaired HTML document. You can just paste that back into your post without having to manually track down errors. This way, you can get back to blogging.

HTML Validator for Windows

While the tools shown so far have been free, the HTML Validator package for Windows is one you have to pay for.  It also works on the desktop rather than online. It also checks PHP, CSS, JavaScript, links and SEO. You can get a free version available if you want to try it out before shelling out for the full version. The advantage of using a desktop version is that your code will stay on your machine. This means more privacy for you.

The advantage of using a desktop version is that your code will stay on your machine. This means more privacy for you.

HTML Cleaners

Going hand in hand with HTML validating is HTML cleaning. HTML cleaners make code easier to read by indenting it and removing extraneous information like CSS styles when you don’t need them. A lot of generated code contains weird formatting, and cleaning HTML makes it easier to deal with. Here are some good HTML cleaners.

Word to Clean Html

If you’re writing your blog posts with Microsoft Word, you know that the HTML Word generates is less than ideal, with all kinds of junk in the code. You don’t want to paste that into your WordPress post. Word to Clean HTML

This online cleaner is pretty simple. Just paste in your dirty code, click the check boxes on the things you want to clean out of your HTML, and press the “Clean HTML” button. You’ll get some pretty-printed code that you can paste into another program to analyze. It’s free, but there’s also a paid membership for people who make heavy use of it with extra features.


DirtyMarkup is another great free online tool. You can clean up your HTML, CSS, and Javascript file. There’s also an API for developers to interface with it.


HTML Tidy website screenshot

This is a classic command-line tool that has been around forever. In fact, many of the HTML tools shown earlier use HTML Tidy to handle the actual code. This open-source project has laid dormant for a while but now it’s been revived. It now handles XML as well as HTML. If you’re comfortable using the command-line, you can just pop open a terminal window or DOS box and check your work quickly.

HTML Tidy Online

If you would rather not deal with the command-line, you can also access a web-based front-end.

FreeFormatter HTML Formatter

FreeFormatter also offers an HTML cleaner. It works the same way as the validator. You paste in your code, and you get it back pretty-printed with your choice of indentation.

WordPress HTML Plugins

WordPress is indispensable for modern blogging. It’s the blogging platform for a lot of people. One key reason for its success is its vibrant developer community. This community has created all sorts of plug-ins. Being a bunch of geeks, they’ve naturally developed some HTML utilities that make life for bloggers so much easier.


While you can manually copy-and-paste every blog post that you have into one of the HTML validators show earlier in this article, that can take a long time. Who really wants to do that if you have hundreds of posts already? Fortunately, there’s a plug-in for you. Validated shows all of your posts and which ones have errors.

Minify HTML

Going from HTML validating to HTML cleaning, Minify HTML takes HTML code and cleans it into something simpler. This speeds up loading. Speeding up loading makes more readers want to stick around. And that means more advertising dollars and better SEO.

LH HTML Cleaner

LH HTML Cleaner is yet another HTML cleaner plug-in for WordPress. This one is unique in that it lets select individual tabs to eliminate. You might want to get rid of any <i> tags in favor of <em>, because it’s not 1996 anymore.

WP Static HTML Output

WordPress is so easy to use, a lot of people use it to build static sites instead of coding it by hand. There’s nothing wrong with that, but webmasters run into a lot of the same problems as bloggers do: dirty code and slow loading. This plug-in takes your WordPress site and spits out a .zip file containing clean HTML. After that you can move it to your own site. You can even automatically deploy your new site to a folder, Dropbox, or FTP server.

Head Cleaner

Head Cleaner cleans tags from the header and footer of the HTML in your posts. It’s a play on words referring to those head cleaning tapes from the days of VHS and cassette. Like the other tools in this collecting, stripping out all the extra HTML code will make the JavaScript and CSS load faster. This is great if you’re using a custom theme that is slowing down users’ load times.


There are a lot of tools to make checking your HTML code a lot easier for bloggers. Try a few and see which ones work for you. Your readers will thank you for it.

Have a suggestion for a HTML tool we didn’t cover already in this list? Please let us know!

Page Last updated: Jun 28th, 2017