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Regex Tester

Test regular expressions live in your browser. Highlight every match, list capture groups, and get a clear error when the pattern is invalid.

All processing happens locally in your browser. Files are never uploaded.

Test string

Introduction

Regex Tester lets you write a regular expression, choose flags, and type a test string. Every match is highlighted inline and listed below with its start and end offsets and any capture groups. Invalid patterns produce a clear error message instead of failing silently. The tool re-runs as you type.

Features

  • Live testing as you type
  • Inline highlighting of every match
  • Lists capture groups per match
  • Supports g/i/m/s/u flags
  • Clear errors for invalid patterns

How to use

  1. 1Type your regular expression in the first box.
  2. 2Add flags such as g or gi in the second box.
  3. 3Type or paste the test string.
  4. 4Read the highlighted matches and the capture-group list.

Frequently asked questions

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