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Regex tester

The tester runs in this tab. Nothing is uploaded.

Test text

Matches

Enter a pattern.

    How to use this tool

    Test a regular expression in this tab. See matches and a replace preview.

    1. Open Regex tester

      Pattern, flags, and a replace field sit on the left. The sample text is on the right.

    2. Enter the pattern

      Type the expression. g is on by default; add i, m, s, or u if you need them.

    3. Paste the subject text

      Matches highlight in the text. A list of captures sits under the preview.

    4. Try a replacement

      Fill the replace field to preview substitutions, then copy a match if you need it.

    How-to guides

    Coding

    FAQ

    Can I test a regular expression here?

    Yes. Type a pattern and sample text. Matches are listed in this tab.

    Is the text uploaded?

    No. The tester runs in this tab. Closing it discards the pattern and text.

    Which flags can I use?

    g, i, m, s, and u. Sticky y is omitted. Invalid patterns show the engine error.

    Can I replace matches?

    Yes. Fill replace to preview a substitution. $1 and $& work as in JavaScript.

    Is there a size limit?

    Yes. Text is capped at 20,000 characters and 200 matches so the tab stays responsive.