Find parser-detected HTML errors, including malformed markup, with a clear explanation of each problem.
CHECK HTML TAGS, SYNTAX & ERRORS
Check HTML tags and syntax online, find parser errors by line and column, and flag missing doctypes, duplicate IDs and images without alt text.
Run the check to see findings by line.
TESTED & REVIEWED
WHY USE IT
Find parser-detected HTML errors, including malformed markup, with a clear explanation of each problem.
Each parser error includes the line and column where it was found so you can correct the source quickly.
The check happens locally in your browser without sending private source code elsewhere.
HOW IT WORKS
Paste a document or fragment into the editor.
Review errors and warnings ordered by their location in the document.
Update the input and rerun validation until the report is clear.
HTML ERROR-FINDING WORKFLOW
Run the browser-based parser check to surface syntax errors that may be hidden by automatic browser recovery.
Open the exact source location reported for each parser error, correct the markup and validate the updated code.
Review additional warnings for a missing doctype, repeated IDs and image elements that do not include alt text.
COMMON QUESTIONS
Paste your document or fragment into the editor and select Validate HTML. The report lists parser-detected errors with line and column numbers. Correct the source, then run the checker again.
The checker identifies and locates likely problems but does not silently rewrite your HTML. This keeps you in control: jump to the reported line, make the correction and validate again.
It reports syntax problems detected by the HTML parser and also checks for a missing doctype, duplicate IDs and images without alt attributes. It is a practical browser-based check, not a replacement for the official W3C conformance checker.
Errors indicate malformed syntax detected by the HTML parser. Warnings identify quality or compatibility concerns that may still render in a browser.
No. It catches a few common accessibility-related mistakes, but a complete accessibility review requires automated and manual testing.
Yes. Import an .html, .htm or .txt file, run the validation, then select a reported problem to return to the relevant line in the editor.
It focuses on HTML parsing and a small set of markup-quality checks. CSS and JavaScript inside the document may be displayed, but they need dedicated syntax, runtime and browser testing.