HTML validation provides quality assurance that your HTML is free from syntax errors.

Before you make your website public for both users and crawlers, you’ll want to make sure there are no hidden issues in your HTML files that provide the structure for your website.

What is HTML validation for?

HTML validation tests comb through your website looking for syntax errors like extra spaces, omitted quotation marks, or tags that weren’t properly closed. These issues can cause your website to function incorrectly, or even cause visible issues.

The process of validating HTML by hand is tedious and repetitive, however there are great tools freely available that can help automate this process for you and bring any errors to your attention.

An easy HTML validation tool provides a validator tool that is as easy as inputting your website address.

Markup Validation Service by W3C
Markup Validation Service by W3C

Once you pop in your domain and hit “check”, the validation scan begins working giving you a list of ‘Warnings’ and ‘Errors’.

Validation warnings and errors
Validation warnings and errors

Each item listed on your report will tell you where the error was found, and why they’ve flagged it as an error.

How to fix HTML validation errors

If you use the W3C validation tool, many of the errors will link to articles that discuss the error in more detail. Because of the long list of errors that can occur, this article can not go into detail about each one.

Start by focusing on the items listed as “errors” (shown in red) first, as those could be causing the most amount of issues.

Don’t be alarmed to find validation issues, even large, popular websites (like Wikipedia) have errors. You’ll likely need to work with a developer to fix all the issues you find.