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Regex Tester

Test a JavaScript regular expression against bounded local text.

Your data is processed locally in your browser and is never uploaded.Maximum: 4 MB per file. Input is not saved in browser storage or placed in the URL.
Output

Patterns are limited to 1,000 characters, test text to 100,000 characters, and results to 1,000 displayed matches. Avoid untrusted, computationally expensive patterns.

How to use this tool

  1. Supply pattern and flags lines, a blank line and test text, then inspect matches.
  2. Review the live result and use Copy result when you need to share it.

How the transformation works

The tool compiles but never evaluates code and limits displayed matches to 1,000. Processing runs entirely in this browser. The page does not upload, persist, execute or remotely inspect the supplied content.

Processing rules

The tool compiles but never evaluates code and limits displayed matches to 1,000. Processing runs entirely in this browser. The page does not upload, persist, execute or remotely inspect the supplied content.

Step-by-step transformation

  1. Supply pattern and flags lines, a blank line and test text, then inspect matches.
  2. The tool compiles but never evaluates code and limits displayed matches to 1,000. Processing runs entirely in this browser. The page does not upload, persist, execute or remotely inspect the supplied content.
  3. Check the displayed result, then copy it if needed.

Worked example

A named word group extracts words of five or more letters with indices.

Risk guidance

Frequently asked questions

Does this tool send my inputs anywhere?

No. The interactive calculation runs in your browser and this site does not submit tool inputs to a backend.

How should I use the result?

Check that the entered units and values match your situation, especially around dates, breaks, and rounding.

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