Skip to content
HeyTools

Developer Tools

Regex Tester

Try a pattern against sample text and inspect matches, indexes, and capture groups instantly. Uses JavaScript RegExp in your browser—nothing is uploaded.

Loading tool…

How to use

  1. Enter a pattern and optional flags
  2. Paste sample text to test against
  3. Review matches and capture groups

Next step

  • Text Diff

    Paste two versions of a document, config, or code snippet and see added and removed lines at a glance. A simple line-oriented diff that stays in your browser.

  • JSON Formatter

    Paste JSON to format, validate, and beautify it instantly in your browser. Free online JSON formatter.

Frequently asked questions

Which regex flavor is used?

JavaScript RegExp, including flags such as g, i, m, s, u, and y. Patterns that work in other engines (PCRE, .NET) may differ slightly.

Is my pattern or sample text uploaded?

No. Matching runs locally. Share links can embed short pattern/text in the URL if you choose to share—avoid putting secrets into shared links.

Why do empty matches stop early?

Zero-length matches advance the lastIndex to avoid infinite loops. Results are also capped so runaway patterns stay responsive in the browser.