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REGEX tester
readyLive JavaScript regular expression tester. Type a pattern and test string - matches highlight as you type.
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Match count: 0 · Groups: -
Pattern error
[01] Common flags
g- global; find all matches (default is just the first)i- case-insensitivem- multiline;^and$match start/end of each lines- dotall;.matches newlinesu- unicodey- sticky; only match fromlastIndex
[02] Engine
Uses your browser's native ECMAScript regex engine via new RegExp(pattern, flags). Supports lookbehinds (?<=…) in modern browsers. For PCRE-only features (recursion, named subroutines), use a server-side regex tool - JustKit can't help.
No signup. Tool input stays in your browser. Your pattern and test string never leave the browser.
Common questions
Is Regex Tester free to use?
Yes. The tool runs in your browser at no cost, with no signup required.
Where is the math performed?
Calculations run locally in your browser. Your inputs do not leave your device.
Are the rates and rules current?
We update sources when published rates change. For high-stakes decisions, verify against the official source linked on this page.