Text Tools
Regex Tester
Test regular expressions against text with match details.
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What is Regex?
A regex playground: enter a pattern and flags, paste test text, and inspect each match with its index and capture groups.
How it works
The pattern compiles into a RegExp with your flags; exec() walks the text collecting matches (with a guard against runaway zero-width loops).
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Pattern validation
Test a pattern against candidate strings to see matches, captures, and flags in real time — the fastest way to debug a regex.
Common mistakes
Catastrophic backtracking
Nested quantifiers like (a+)+ can hang on certain inputs. The tester warns when a pattern risks pathological behavior.
Frequently asked questions
Which regex flavor is used?
JavaScript (ECMAScript) syntax, with flags for global, case-insensitive, multiline, and dot-all.
Can I see capture groups?
Yes — every match highlights its groups and named captures.