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Regex Tester & Cheatsheet

Time & Logic

Test JavaScript regular expressions against text payloads with real-time match details and capture groups.

Flags:
//gm
Presets:
Test String / Payload
Matches are evaluated live5 lines · 179 chars
Match Results3 matches
Match #1: "PROJ-1024"Index 22
Capture Groups:
Group 1:1024
Match #2: "DEV-452"Index 63
Capture Groups:
Group 1:452
Match #3: "BUG-99"Index 107
Capture Groups:
Group 1:99
Guide & Documentation

Regular Expression Live Matcher, Flag Studio & Syntax Cheatsheet

Test regular expressions with instant real-time match highlighting, capture group extraction, and regex flag toggles (g, i, m, s, u). Includes a built-in developer syntax cheatsheet.

How to Test Regular Expressions

01

Write Regex Pattern

Input your regex expression and toggle flags like global (g), case-insensitive (i), or multiline (m).

02

Provide Test Text

Paste the corpus text, logs, or string payloads you need to search or validate against.

03

Inspect Visual Matches & Groups

Review highlighted match segments and indexed capture group values extracted instantly.

Regex Tester Features

Real-time Match Highlighting

Color-coded highlights show exact character spans matched across multiple text lines.

Built-in Syntax Cheatsheet

Quick reference for lookaheads, lookbehinds, non-capturing groups, character classes, and anchors.

Capture Group Breakdown

Dissects capture groups $1, $2, etc., allowing developers to test regex replacements effortlessly.

Regular Expression Best Practices

  • §1Beware of catastrophic backtracking (ReDoS) with nested quantifiers like (a+)+ on untrusted user input.
  • §2Use non-capturing groups (?:...) when you don't need to extract specific substring variables to boost speed.
  • §3Anchor your patterns with ^ and $ when validating complete inputs like emails, UUIDs, or phone numbers.

Frequently Asked Questions

Which regex engine does this tool use?
It uses the browser's native JavaScript (ECMAScript) RegExp engine, supporting Unicode property escapes, named capture groups, and lookbehind assertions.
What does the 's' (dotAll) flag do?
The 's' flag enables dotAll mode, causing the '.' wildcard character to match newline characters (\n, \r) as well.
Is my test text processed privately?
Yes, all regular expression evaluations run strictly in-memory in your browser. No strings are uploaded.

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