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Regular Expression
/ /
Test String
Match Results
Match Details
📖 How to Use RegexLab

Step 1: Type your regex pattern in the input field (without surrounding slashes).

Step 2: Toggle flags — g finds all matches, i ignores case, m enables multiline.

Step 3: Paste your test string. Matches highlight instantly with color-coded capture groups.

Step 4: Review match details below. Click 🔗 Share to send your pattern to a teammate.

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📚 Need quick references?

Developer cheat sheets for interviews, DevOps, SQL, and more. Instant PDF download.

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Quick Reference
.Any character
\dDigit [0-9]
\wWord char [a-zA-Z0-9_]
\sWhitespace
^Start of string
$End of string
*0 or more
+1 or more
?0 or 1
{n,m}n to m times
(abc)Capture group
(?:abc)Non-capture group
[abc]Character set
[^abc]Negated set
a|bAlternation
(?=a)Lookahead
(?<=a)Lookbehind
\bWord boundary
❓ Frequently Asked Questions
What is a regex tester?

A regex tester lets you write regular expressions and instantly see matches against test text. RegexLab highlights matches in real-time, shows capture groups, and runs 100% in your browser.

How do regex flags (g, i, m, s, u) work?

g finds all matches. i ignores case. m treats each line separately. s lets . match newlines. u enables full Unicode support.

What are capture groups?

Parts enclosed in () that extract specific portions of a match. For example, (\w+)@(\w+) captures username and domain separately. Use (?:...) for non-capturing groups.

Is this tool free and private?

Yes. Completely free, no account required. All processing runs in your browser — your test data never leaves your device.

Can I share my regex with my team?

Click 🔗 Share to generate a URL encoding your pattern, flags, and test string. Anyone who opens the link sees your exact setup restored.

What regex engine does RegexLab use?

Your browser's native JavaScript RegExp engine (ES2018+), supporting lookbehind assertions, named capture groups, and Unicode property escapes.

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