Free Developer Tool
Regex Tester & Debugger
Test and debug regular expressions with live matching, capture group highlighting, replace mode, and a common patterns library. 100% Browser-Based
Quick Usage Guide
1. Write Your Pattern
Enter a regex pattern and toggle flags (global, case insensitive, multiline, dotsall, unicode). Matches highlight in real time.
2. Inspect Matches
View all matches with their index, length, and capture groups. Each group gets a distinct color for easy identification.
3. Replace & Share
Switch to Replace mode to test substitutions with backreferences. Use the share link to save or send your regex.
Regex 101
What is Regex?
Regular expressions (regex) are patterns used to match character combinations in strings. They are powerful tools for searching, validating, and manipulating text across virtually every programming language.
Capture Groups
Parentheses () create capture groups
that extract parts of a match. Use $1,
$2 in replacements to reference them.
Named groups use (?<name>...).
Flags Explained
g finds all matches,
i ignores case,
m makes ^ and $ match line boundaries,
s lets . match newlines,
u enables full Unicode support.
100% Client-Side
All regex processing happens entirely in your browser using JavaScript's native RegExp engine. Your data is never sent to any server. You can verify this by disconnecting from the internet.
Regex Quick Reference
| Pattern | Description | Example |
|---|---|---|
| . | Any character (except newline) | a.c matches "abc", "a1c" |
| \d, \w, \s | Digit, word char, whitespace | \d+ matches "42", "123" |
| [abc] | Character class (a, b, or c) | [aeiou] matches vowels |
| ^, $ | Start / end of string (or line with m flag) | ^Hello matches "Hello world" |
| *, +, ? | 0+, 1+, 0 or 1 repetitions | colou?r matches "color", "colour" |
| {n,m} | Between n and m repetitions | \d{2,4} matches 2-4 digits |
| (group) | Capturing group | (ab)+ matches "abab" |
| a|b | Alternation (a or b) | cat|dog matches either |
Common Use Cases
Input Validation
Validate email addresses, phone numbers, URLs, and other structured inputs before they reach your backend. Test patterns against edge cases.
Log Parsing
Extract timestamps, error codes, IP addresses, and user IDs from server logs. Build and test extraction patterns before coding them.
Find & Replace
Refactor code, transform data formats, or clean up text with regex-powered find and replace. Preview results before applying changes.
Streamline Your Development Workflow
From code formatting to deployment pipelines - we build custom developer tools, CI/CD automation, and internal platforms that boost your team's productivity. Let us help you eliminate repetitive tasks and ship faster.
Optimize Your Workflow