Regex Tester

Test JavaScript regular expressions with live highlights and capture groups.

About this tool

Test JavaScript Regular Expressions Live

Every match is highlighted as you type, and the list shows each match with its capture groups. The flags are explained in plain words, so you know what g, i, m, s, u and y do.

How to use it

  1. Type the regular expression and switch the flags you need on.
  2. Paste the text to test, or drop a file.
  3. Check the highlighted matches and groups, and copy the matches.

Frequently asked questions

Is my data sent anywhere?

No. Every tool runs in your browser. Tokens, passwords and files are processed on your device and never uploaded.

Can I link to a tool?

Yes. Each tool has its own address, for example toolula.com/dev/regex-tester, and you can star tools to keep them at the top of the list.

Does the JWT decoder check the signature?

No. It decodes the header and payload and shows their dates; checking the signature needs the secret or public key.

Are the generated passwords and UUIDs random enough?

Yes. They come from the browser's cryptographic random generator (crypto.getRandomValues / randomUUID), the same source used for keys.