TOOL · 07
Regular Expression Tester
Write a pattern, paste your text — matches highlight live as you type, with index positions and capture groups.
Pattern
Output
About regular expressions
A regular expression is a pattern language for matching text — email addresses, dates, log lines, almost anything. This tester uses your browser's native JavaScript RegExp engine with live feedback, supports the g, i, m and s flags, and shows every capture group. Nothing you type leaves the page.
Features
Live matching
Matches highlight as you type — no run button needed.
Capture groups
Every group of every match, listed with its index.
Flag support
Toggle the g, i, m and s flags with one click each.
100% private
Uses your browser’s native RegExp engine — nothing uploaded.
How to use
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1
Write a pattern
Type a regular expression in the pattern field.
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2
Paste test text
Drop in the text you want to match against.
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3
Read the results
Highlighted matches, counts, positions and capture groups update live.
Use cases
Email validation
Build and test patterns that match email addresses.
Log parsing
Extract fields from structured log lines.
Find & replace prep
Dry-run a pattern before running it in your editor.
Learning regex
See exactly what each part of a pattern matches.
Example
\b[\w.+-]+@[\w-]+\.[a-z]{2,}\bpostmaster@tmpio.com
support@example.orgThe pattern uses the same JavaScript RegExp syntax your browser uses — what you test here behaves identically in your code.
FAQ
Which regex flavor is this?
JavaScript (ECMAScript) regular expressions, executed by your browser’s native engine — the same as new RegExp() in your code.
Why do I see “Invalid pattern”?
The pattern has a syntax error — an unclosed bracket or quantifier, for example. The message shows where the engine gave up.
What do the flags do?
g finds all matches (not just the first), i ignores case, m makes ^ and $ work per line, and s lets . match newlines.