Due to lack of resources to maintain the underlying project, W3C is planning to stop providing this on-line service as of 31 March 2023.

Nu Html Checker is now the default, for markup other than HTML5 you may use the legacy Markup Validator through custom task settings.

Select a task

Performs as many checks as possible.

Validate by URI

Enter the URI of a document you would like checked

Validate by File Upload

Choose the document you would like checked

Validate by Direct Input

Enter the document you would like checked