Skip to main content
CompressNConvert

Regular Expression Tester

Test JavaScript regex patterns, flags, matches, and capture groups in real time.

Runs locally in your browser

//gim
Valid pattern

Match details

Global matching is always enabled · capped at 500

  1. No matches found.

Complete tool guide

Regular Expression Tester guide

This tester compiles patterns in an isolated browser worker, lists every match with its offset and capture groups, and stops evaluations that exceed the time budget.

Your input is processed in the current browser tab and is not sent to the application server.

Why use this tool?

  • Inspect or transform developer data without installing another utility.
  • Copy a clean result directly into code, a terminal, an API client, or documentation.
  • Keep routine developer work in one fast, consistent interface.

Common use cases

  • Developing input validation and parsing patterns
  • Extracting values from logs or test fixtures
  • Checking capture groups before adding a regex to code

How to use it

  1. 1

    Enter a JavaScript regex without surrounding slashes.

  2. 2

    Enable the flags needed by the pattern.

  3. 3

    Paste representative test text.

  4. 4

    Review every match, offset, and captured group.

Global matching

The tester always adds the g flag so it can find every non-overlapping match.

JavaScript syntax

Features and escaping follow the regular expression implementation in your browser.

Empty matches

Patterns that match an empty string are advanced by one position to prevent an infinite loop.

Practical tips for better results

  • Test expected matches and values that must not match.
  • Avoid nested ambiguous quantifiers that can cause excessive backtracking.
  • Prefer readable smaller patterns over a single expression that handles every rule.

Frequently asked questions

Does the Regular Expression Tester upload my data?

No. The transformation runs locally in your browser. Avoid pasting secrets into any tool you do not control, and clear the fields when using a shared device.

Can I use the result in production?

You can copy or download the result, but review it in the context of your application and run the project-specific tests or validation required by your workflow.

Keep working

Related dev tools

Continue with another focused tool from the same collection.

Diff CheckerCompare text or code line by line, or normalize JSON for a semantic structural comparison.URL Parser & ValidatorValidate absolute URLs and inspect schemes, hosts, paths, query parameters, credentials, and fragments.User-Agent ParserIdentify browser, engine, operating system, device class, and CPU hints from a User-Agent string.HTTP Header ParserParse pasted HTTP headers and group security, caching, content, CORS, and general fields.