Regular Expression Tester

Test JavaScript regular expressions with real-time match highlighting and capture groups.

About this tool

Develop and debug complex regular expressions with instant client-side evaluation.

How to use this tool

  1. Enter regex pattern and flags
  2. Paste test string
  3. Inspect match results and capture groups

How it works

Executes RegExp pattern matching in browser memory and captures match offsets and groups.

When to use this tool

  • Validating email regex patterns
  • Extracting tokens from log files

Frequently asked questions

Are lookahead and lookbehind supported?

Yes, modern ECMAScript regex lookarounds are supported.

Limitations

Catastrophic backtracking patterns are guarded by browser execution limits.

Privacy

Input text is never transmitted.