Regex Tester
Test regular expressions with real-time matching and group highlighting
What is the Regex Tester?
Written and maintained by the BitConvert team · Feb 27, 2026
The Regex Tester lets you build a regular expression and run it against sample text with results that update as you type. A regular expression is a compact pattern language for matching character sequences, and this tool uses JavaScript's native RegExp engine, so the behavior you see here matches exactly what your JavaScript, TypeScript, or Node.js code will do.
As you edit the pattern or the test string, every match is highlighted directly in the text, and a details panel lists each match along with its captured groups, including named groups, and their positions. You can toggle the standard flags to change matching behavior: g for global (find all matches), i for case-insensitive, m so that ^ and $ anchor to line boundaries, s (dotAll) so the dot matches newlines, and u for full Unicode support. All processing happens locally in your browser, so nothing you type is uploaded anywhere.
Key Features
Live Highlighting
Matches light up inside your test string the moment you change the pattern or the sample text, with no button to press.
Capture Group Breakdown
Each match lists its numbered and named capture groups along with their values and positions for precise debugging.
Full Flag Control
Toggle the g, i, m, s, and u flags to switch between global, case-insensitive, multiline, dotAll, and Unicode matching.
Native JavaScript Engine
Patterns run on the browser's built-in RegExp, supporting lookahead, lookbehind, named groups, and Unicode properties.
Common Use Cases
Prototype and validate a pattern for emails, phone numbers, slugs, or URLs before dropping it into production code. Diagnose why an existing regex is over- or under-matching by testing it against real sample data. Extract fields from log lines or CSV rows using capture groups and confirm the exact substrings you capture. Experiment interactively to learn quantifiers, anchors, and character classes. Refine find-and-replace patterns for editors and build scripts.
How It Works
Enter Pattern
Type your regular expression pattern
Add Test String
Enter text to test against your pattern
See Matches
Matching parts are highlighted with group details
Frequently Asked Questions
Last updated: Feb 27, 2026