Regex Tester & Debugger

Enter a regex pattern and test string and see all matches in real time. Shows capture groups, match indices and supports all JavaScript regex flags (g, i, m, s, u).

100% freeNo sign-upRuns in your browserNo upload · data stays private

📖 Read the full Regex Tester & Debugger guide — how it works, examples & FAQ →

How to use this tool

  1. Paste your test string.
  2. Enter a regex pattern.
  3. Set flags (g i m s u) and read the matches.

Example

/(hel+o)/gi on "hello world hello" → 2 matches: [0] "hello", [12] "hello"

Why it's private

This tool runs entirely in your browser using JavaScript. Whatever you paste is processed on your own device — it is never uploaded to a server, logged, or stored. Built by Calabi, which also strips AI metadata and C2PA signals from images and video.

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