Code Tools

W3Schools Code Validator (local)

W3Schools Code Validator (local) — a local code checker for JavaScript, JSON, CSS, and HTML. It is free, private, and runs in your browser.

Client-sideRuns entirely in your browser — your data never leaves your device.

W3Schools® is a trademark of Refsnes Data. This independent browser tool is not affiliated with or endorsed by W3Schools, and trademarks belong to their respective owners.

Code input
Validation report



  
How to use W3Schools Code Validator (local)

  
    
      
  1. Paste the text you need to validate into the input box.
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  2. Set Language so the output fits your use case.
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  3. Watch the output update instantly while you adjust the text.
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  4. Use Copy to keep or reuse the result.
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About this tool

  
Everything W3Schools Code Validator (local) does happens on your own device. W3Schools Code Validator (local) is a free Code Tools utility that runs in your browser, doing its work on the input you provide without a backend.

  
It is designed to do one job well and stay out of your way. Nothing you enter is uploaded, and it keeps working offline once the page has loaded.

  
Frequently asked questions

  

      
What is W3Schools Code Validator (local) for?
W3Schools Code Validator (local) lets you validate your input right in the browser using the Language control, with the result shown instantly and nothing uploaded.

      
Is W3Schools Code Validator (local) free to use?
Yes — W3Schools Code Validator (local) is completely free, with no usage limits.

      
Does W3Schools Code Validator (local) upload my data?
No — W3Schools Code Validator (local) processes everything locally in your browser, so nothing you enter is uploaded or stored.

      
Can I use W3Schools Code Validator (local) without a connection?
Yes — after the first load W3Schools Code Validator (local) runs entirely offline.

  

  
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