Regex Tester

What it does

Runs your regular expression against your test string and returns matches, capture groups, named groups and positions, and it detects catastrophic-backtracking (ReDoS) patterns and refuses to run them instead of hanging.

How it works

1. Provide your pattern and a test string.
2. Pay $1: by card, or with x402 if you’re an AI agent. No account, no signup.
3. Get matches, capture groups, named groups and positions back, or a plain warning if the pattern is the dangerous shape.

Why it’s worth $1

A free console will happily execute the one pattern that takes your server down and tell you nothing. This one detects the dangerous ReDoS shape and refuses it, so you learn the pattern is unsafe before it ships to production.

Frequently asked

What flavor of regex?

Common PCRE-style syntax: character classes, quantifiers, capture and named groups, anchors.

What counts as a dangerous pattern?

Patterns prone to catastrophic backtracking (nested quantifiers over overlapping classes): the classic ReDoS shapes.

Is my input stored?

No. The pattern and test string are used for the single run and not saved.