HTML Validator

HTML Validator

This is a free online tool that lets you validate HTML code against W3C standards. This HTML validator shows all errors, warnings, and suggestions and helps you write the correct HTML code. It is the best HTML syntax checker or HTML code checker available online.

Created by Commontools | Updated on: September 28, 2023


Error and Warnings


Businesses and people need an online presence as the digital landscape changes rapidly. Web developers, startups, companies, or even individuals like us strive for interesting, error-free websites, but perfection is really difficult, and that's too, if you want to save development time. This is where our HTML Validator helps.

Now, let's check out the motivation and inspiration for creating this tool.

Motivation for the creation of the Tool

Our motive for designing this online HTML Validator tool was to ease the process of validating HTML code and make it available for free to everyone who can't afford the premium or paid tools. 

Also, we know that detecting errors and warnings in complicated HTML might be difficult for non-coders or individuals who just started coding. We wanted to create a solution for everyone, regardless of technical ability.

First, let's clarify the meaning of the tool.

What is the HTML Validator Tool?

HTML Validator Tool is a tool created by for efficiently validating your HTML code and checking errors and warnings against the rules set by W3C. In simple words, it scans the HTML code and checks errors and warnings. This helps you identify and rectify issues that might affect your website's performance or user experience.

How do I Validate HTML Online?

Here are step-by-step instructions you should follow for using our "Online HTML Validator Tool" and validating your HTML code online for free:

Step 1: Access the Tool

  • Visit the HTML Validator tool, created by on Google, or search for it by visiting our website.

Step 2: Input HTML Code

  • In the "Input" section of the tool, you can either:
    • Directly type it or paste your HTML code into the large text editor labeled "Input" OR
    • Click on the "Upload" button to select an HTML file from your computer. Our tool will automatically fetch your code from the file and insert it into the Input text area.

Step 3: Upload an HTML File (Optional)

  • If you choose to upload your file:
    • Click the "Upload" button.
    • A file dialog will populate; just select the HTML file you want to validate. And then click the open button.
    • The contents of the file will be loaded into the input editor.

Step 4: Validate HTML

  • After entering your HTML code or uploading a file, click the "Validate HTML" button.
  • You will see a "Validating..." message while our tool processes your HTML code and shows you all the errors and warnings.

Step 5: View Validation Results

  • Once the validation is complete:
    • If your HTML code is error-free (which means it has 0 errors), you will see the message "Valid HTML." This signifies you have done a great job, and the code is free from all the errors and sticks to the rules and guidelines set by the World Wide Web Consortium (W3C).
    • If your HTML code has errors or warnings, you will see a message indicating the number of errors and warnings found.

Step 6: Review Errors and Warnings

  • Scroll down to the "Error and Warnings" section. 
  • You will find a detailed table that lists the details of each error or warning found in your code:
    • "Line": The line number where the issue is found.
    • "Col" (Column): The column number within the line where the error or warning is found.
    • "Type": It indicates whether it's an error or warning. Errors mean you must resolve them.
    • "Description": Provides a message describing the error or warning in detail so that you can work on it.

Step 7: Clear Input (Optional)

  • If you wish to clear the HTML code from the input editor and want to start fresh, just click the "Clear" button. It's simple.

Step 8: Copy Input (Optional)

  • Click the "Copy Input" button to copy the HTML code from the input editor to your clipboard.

Step 9: Copy Output (Optional) [We are working on this feature]

  • Click the "Copy Output" button to copy the HTML code displayed in the input editor to your clipboard.
  • The button will briefly change to "Copied!" to indicate successful copying.

That's it! 

Example Output

Let's see how our HTML Validator tool gives output:


3 errors and 0 warnings found.

Line Col Type Description
10 undefined error Saw “<” when expecting an attribute name. Probable cause: Missing “>” immediately before.
10 undefined error A slash was not immediately followed by “>”.
10 undefined error End tag had attributes.
2 16 info Consider adding a “lang” attribute to the “html” start tag to declare the language of this document.


Our HTML Validator tool has several useful applications for diverse user groups. Let's see, check out some of the top.

Web Developers

This tool helps web developers and coders confirm that their HTML code meets industry standards. It detects coding problems rapidly and helps you create well-structured and user-friendly websites.

Creators of Content

The tool also lets bloggers, authors, and content creators evaluate HTML formatting for blog postings. It ensures that their content displays correctly and consistently across different devices (Mobile, Desktop, and Tablets) and browsers.

Students and Beginners:

Our tool helps web development students and beginners write clean HTML code and learn from their mistakes. This is really important for beginners.

Website owners

It helps website owners check for problems that could affect functionality or SEO when making content modifications. This is really important from the ranking perspective on modern search engines.


Key features of our HTML Validator tool that make it ideal for web developers and newbies:


You can use our tool for free. Everyone can use it. There is no need to spend a penny to validate your code.


Results are available in seconds after validation. Yes, just after a mouse click, you will see the results of validation.


This tool or utility is accessible from any internet-connected device without installation. Yes, you hear it right. You do not need to install anything. Just visit the tool URL and start using it.

No Signup or Login Required

You can use our tool without registering and entering any personal details. We respect your privacy and convenience. Without making an account, you can use the tool instantly. No signup or login required.

Supported on All Browsers

Available on All Browsers! Our tool works effortlessly on popular web browsers, assuring cross-platform compatibility so that you can work with the browser of your choice.

Easy-to-Use Interface

Both beginners and expert developers can use the tool's user-friendly interface. It's super easy and works on Desktops, Tablets, and Mobiles.


Our tool uses W3C Markup Validation Service, a trusted HTML validation source, for accurate results.

Various Options

Our tool supports various options. You can Enter HTML code directly or upload a file, copy input and output, easily clear input, and many more.

Above are just a few features our tool offers. Trust us; once you start using it, you'll discover many more.


A well-structured and error-free website is essential for success in the digital age. It's now super easy to validate your HTML code using our free, user-friendly online HTML Validator. This tool assures that your HTML code is error-free and adheres to the rules and guidelines set by the World Wide Web Consortium (W3C). You can efficiently check your code for errors and warnings and can save plenty of development time. And the best part is that it's completely safe and free, with no need for a login.


Cite this tool

Use the citation below to add this tool to your bibliography:



MLA Style Citation

"HTML Validator.", 2024. Sat. 13 Jul. 2024. <>.

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