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Free developer tool

CSS Validator

Catch syntax errors, invalid properties, and compatibility issues in your CSS. Paste your code or a stylesheet URL on the left and get instant validation results.

Working field

Validate CSS from a URL or paste it directly.

Validate CSS from URL
Validate Direct CSS Code

Result

Your validation summary appears here.

Your validation summary will show here once you validate CSS from a URL or paste it directly.

This tool is best for catching CSS errors and compatibility issues before you ship to production.

Why Use Our Free Online CSS Validator Tool?

Clean, valid CSS keeps your layouts consistent and helps your SEO. This tool quickly flags syntax errors, deprecated properties, and compatibility issues. It keeps the workflow simple: validate on the left, supporting content below, and the sidebar on the left for popular and related tools.

Catch errors fast

Spot missing semicolons, unmatched braces, and invalid properties before they break your layout.

URL or direct input

Validate a pasted snippet or fetch an external stylesheet straight from its URL.

Better compatibility

Find deprecated features so your styles render consistently across browsers and devices.

Private by design

Your CSS is processed in real time and never stored or shared.

How it works

  1. Paste a stylesheet URL and click Validate URL, or paste CSS directly into the textarea.
  2. Click Validate CSS to check your pasted code for errors.
  3. Review the valid or invalid badge, character count, and any errors in the result panel.
  4. Fix the issues, then re-validate to confirm your stylesheet is clean.

Best practices

  • Validate your CSS before minifying it for production.
  • Fix every reported error to avoid broken layouts.
  • Check external stylesheets you did not write before reusing them.
  • Use the sample code to see how a valid result looks.
  • Re-validate after each round of edits to confirm fixes.
  • Keep a clean, formatted copy of your CSS for easier reviews.

Frequently asked questions

What types of CSS errors can this validator find?

The validator checks for syntax problems like missing semicolons, unmatched braces, invalid properties, and unsupported features that could cause rendering issues across browsers.

Should I validate my CSS before minifying?

Yes, it is highly recommended. Fix any errors here first, then run the clean code through the CSS Minifier to optimize the file for production.

How can I edit minified CSS that has errors?

If your compressed CSS has issues, use the CSS Unminifier to make it readable, fix the errors, and then re-validate the result here.

Does the tool save or share my CSS code?

No. Your CSS is processed in real time and is never stored or shared, so your code stays completely private throughout the check.

Can I validate CSS from a URL?

Yes. Paste a stylesheet URL into the URL field and click Validate URL. The tool fetches the file and checks it for you in seconds.

Does this tool work on mobile devices?

It does. The validator is fully responsive and runs in any modern browser, so you can check CSS on desktops, laptops, tablets, and phones.

For more CSS work, try the CSS Minifier tool to compress your validated stylesheet, or the CSS Unminifier tool to make compressed code readable before fixing errors.