Properly written code is crucial to have, in order to create a functional website. However, checking HTML files by yourself is time-consuming. To make this task more efficient, you can start using an HTML code validator. In this article, we will show you five of our favorite free online HTML code validators.

What is an HTML Code Validator?

HTML code validators are programs that proofread HTML documents. These tools can detect syntax errors like extra spaces and missing quotation marks. For quality assurance, code validators usually refer to the Worldwide Web Consortium’s standard.

Checking for mistakes in your HTML files is important. An invalid code will result in issues on your website.

Choosing an HTML code validator may be difficult since there are many options. Below are our favorite picks.

The Best Online HTML Code Validators

To help you choose the best HTML code validation, we gather a list of the best ones on the web.

1. W3C Markup Validation Service

W3 HTML Validator

Worldwide Web Consortium’s code validator can read multiple file types, including HTML, XHTML, SVG, SMIL, and MathML. Before checking your code, you can choose the encoding of the file.

W3C markup validation service lets you upload your files or paste code directly. What is more, you can input your site’s URL.

Even though the validator service cannot detect broken links, it gives you suggestions on how to improve your code. Opening the links in the recommendations will take you to a relevant article in W3C’s database.

2. Free Formatter

Freeformatter HTML Validator

You can paste your code and upload files to Free Formatter to check it. The online validator supports HTML, SVG, ITS, and RDFa Lite files. Like W3C markup validation service, Free Formatter also allows you to choose the file encoding.

3. JSON Formatter

JSONFormatter HTML Validator

JSON Formatter’s HTML validator offers an interface with two columns. The left one shows your file, while the right one displays the errors.

To start using JSON Formatter, you can upload a file, paste code, or type an URL. The online validator not only can check for mistakes but also fix your code instantly. You can even execute it, to see how it looks like from the frontend. Additionally, you may download the code as a new file.

4. Nu HTML5 Validator

Nu Validator HTML Validator

Nu Validator is a simple online HTML code validator. To use it, you only need to input your HTML file, URL, or paste the code. You may choose to display textual alternatives for images and the markup source of the document. Like W3C markup validation service, Nu Validator also gives a relevant article to fix your mistakes.

5. Online Toolz HTML Validator

Online Toolz HTML Validator

Online Toolz HTML is another online HTML code validator, however, it has limited functions. It only supports pasting your code as the input method.

To make up for that, the website also has many other tools, including a script that formats your HTML code.


Online HTML validators are useful when you want proper code on your website. Some of them also help you to better your coding skills.

The HTML code validator of our choice is W3C because of its great functionality and easy to use interface.

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