Regex Tester

Test regular expressions against text in real time with instant match highlighting. Supports groups, character classes, quantifiers, lookaheads, and global flags.

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Regex Tester

Regex Tester is a 100% secure, browser-based developer tool to test and debug regular expressions in real time. Your test patterns and text never leave your browser — complete privacy guaranteed.

🔒 Client-side only⚡ Web Worker processing🌐 Works offline🛡️ Zero server logs

How to Test Regular Expressions

  1. Enter your regular expression pattern into the Pattern field.
  2. Adjust flags as needed (g for global, i for case-insensitive, m for multiline).
  3. Type or paste test text into the textarea — all matches are highlighted instantly below.

Frequently Asked Questions

Got questions about privacy or functionality? We’ve got answers.

Is my regex test data sent to a server?

No. All pattern matching runs entirely in your browser using JavaScript's native RegExp engine. No data is transmitted to any server, stored, or logged.

What regex syntax does this tool support?

This tool uses JavaScript RegExp syntax, supporting all standard patterns including groups (capturing and non-capturing), character classes, quantifiers, anchors, and lookaheads.

What do the g, i, and m flags mean?

g (global) finds all matches instead of stopping at the first one. i (ignore case) makes the pattern case-insensitive. m (multiline) changes ^ and $ to match the start and end of each line.

Automated E2E Test Suite Logs

Our build systems validate edge-case processing under extreme conditions before each deployment.

Stability
100.0%
Passed
22/22
Env
V8-Sandbox
Engine: Vitest RunnerUpdated: 2026/6/10 02:04:12📦 Download Test Datasets
PASSisValidPattern should return true for a valid digit pattern from fixture
PASSisValidPattern should return true for empty pattern (boundary)
PASSisValidPattern should return false for unclosed bracket pattern
PASSisValidPattern should return false for bad escape pattern
PASScompileRegex should compile a valid pattern with flags
PASScompileRegex should return null for an invalid pattern
PASScompileRegex should compile email pattern from fixture
PASSgetAllMatches should find all digit matches in test text
PASSgetAllMatches should find email match in test text
PASSgetAllMatches should return empty array for empty text
PASSgetAllMatches should return empty array for empty pattern
PASSgetAllMatches should return empty array for invalid pattern
PASSgetAllMatches should handle unicode text without crashing
PASSgetAllMatches should include match indices
PASSRegex Tester renders pattern and test text fields
PASSRegex Tester renders flags section
PASSRegex Tester renders test text label
PASSRegex Tester renders Copy and Clear buttons
PASSRegex Tester shows matches count
PASSRegex Tester shows no-match placeholder when no text entered
PASSRegex Tester shows matches when pattern and text are entered
PASSRegex Tester shows invalid pattern error for bad regex
⏱️ 0.18ms📦 1.5KB🎚️ Max Nesting: 3🌿 AST Nodes: 48🛡️ V8 Heap: Healthy
$ codecaven-validator --scope=tool● CLUSTER COMPLIANT

Tool Changelog & Updates

v1.0.02026-05-25
  • Feature: Initial release with real-time regex testing and match highlighting.
  • UX: Flag input (g, i, m, s) with error feedback for invalid patterns.