DevToolMage

Patterns

Regex Tester

Run a JavaScript RegExp against sample text and inspect matches and groups. It is not a multi-engine debugger.

This tool can receive sensitive values. Processing stays in your browser. Do not paste production secrets, private keys, or live access tokens. DevToolMage does not upload or log the input.

JavaScript flags

Matches

2 matches. JavaScript flavor only.

  1. 1. [9] mage@example.com groups: mage, example.com
  2. 2. [30] ops@example.org groups: ops, example.org

How it works

Constructs new RegExp(pattern, flags) and walks matches with a lastIndex guard. Named groups are listed when present.

Input and output

Input is a pattern, flags, and test text. Output is match spans, groups, and errors.

Examples

Email-shaped

A simple capture pattern can extract the local part and domain from a sample, not from all real addresses.

Invalid pattern

Unbalanced parentheses produce a syntax error, not a hang.

How to use this tool

  1. Enter a pattern without slashes.
  2. Set flags.
  3. Paste test text and read matches and groups.

Limitations

  • JavaScript flavor only.
  • Does not explain PCRE-only syntax.
  • Does not share patterns to a server.

Questions

Does this support PCRE or Python regex?

No. It uses the JavaScript engine in your browser. Recursive patterns and possessive quantifiers are not available.

Can a pattern freeze the tab?

Catastrophic backtracking is still possible. The tester caps match iteration. Prefer simpler patterns on large text.

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