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Regex Tester

Test regular expressions with live highlighting and groups.

Free, no uploads, no sign-up. Runs 100% in your browser.

How Regex Tester works

Regex Tester runs entirely in your browser. Test regular expressions with live highlighting and groups. Under the hood it uses Web Worker (runs your regular expression in a background thread so a catastrophic pattern cannot freeze the page). Your files are read into this tab’s memory, processed on your own CPU, and handed back to you as a download. Nothing is sent to a server.

How to use Regex Tester

1. Open Regex Tester and paste or type your input.
2. Results update instantly as you type.
3. Tweak options such as format, indentation or algorithm.
4. Copy the output or download it as a file.

Tips

• Everything is computed locally. Safe for tokens, keys and private data.
• Use Ctrl/⌘ + K to jump between developer tools quickly.

Regex Tester FAQ

Are my files uploaded?

No. This tool runs entirely in your browser tab. Files are read from your disk into memory and the result is generated locally.

Is it free? Are there limits or watermarks?

Free and open source (MIT). There are no file-size caps, daily quotas, accounts or watermarks.

Does it work offline?

Yes, once the page (and any engine it needs) has loaded, it keeps working without a connection thanks to the service worker cache.

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