Check a new HTML section
Send the active HTML to the online W3C validator and review its messages.
Check page markup
Check the code after a page edit.
You added a section and want to catch markup problems. Run validation, inspect each message and correct the relevant source.
What you can do
Use it on your own website.
Check a page’s markup, fix the reported issues and review the result before publishing.
Check XML content locally
Use As XML to check XML-style content locally for well-formedness.
Return to the source and fix it
Use the results alongside the editor, then run the check again after corrections.
Getting started
Make this update.
You added a section and want to catch markup problems. Run validation, inspect each message and correct the relevant source.
- Choose the document — Open the HTML or XML-style document to check.
- Run validation — Review the reported messages for the active source.
- Correct and check again — Fix relevant issues and inspect the rendered page.
Useful details
Questions about this task.
Check how this works with your project and hosting.
Does validation send my document online?
The W3C check sends the active source to the online validator and needs a connection. As XML runs locally, but checks XML well-formedness rather than HTML conformance.
Does a clean result mean the website is ready in every respect?
No. Markup validation does not test every link, script, screen size or accessibility requirement. Review the page and its interactions as part of your publishing workflow.