This free online regex tester lets you write, test, and debug regular expressions in real-time with visual match highlighting and a detailed match table. Whether you're validating email patterns, parsing log files, or extracting data from strings, this regular expression playground includes 8 built-in presets and full flag support for the JavaScript regex engine.
Step-by-Step
1. **Enter your regex pattern** in the pattern field at the top.
2. **Paste test text** into the input area below.
See matches highlighted — All matches are highlighted in real-time as you type. A match table shows each match with its index, value, and captured groups.
Toggle flags — Enable or disable global (g), case-insensitive (i), and multiline (m) flags.
Try presets — Click any of the 8 built-in preset buttons to load common patterns instantly.
Features
Real-time highlighting — Matches are highlighted in the test text instantly as you modify the pattern.
Match table — See every match listed with its position, full match value, and captured groups.
8 built-in presets — Email, URL, IPv4, phone number, date, hex color, HTML tag, and credit card patterns ready to use.
Flag toggles — Global, case-insensitive, and multiline flags with visual toggle buttons.
Match counter — Shows the total number of matches found.
Group extraction — Named and numbered capture groups are displayed in the match table for easy inspection.
Error detection — Invalid regex syntax is caught and displayed as a clear error message.
Client-side engine — Uses JavaScript's native RegExp object. No server calls.
Common Use Cases
Input Validation — Build and test regex patterns for email addresses, phone numbers, postal codes, and custom formats before implementing them in your application's form validation.
Log File Parsing — Write patterns to extract timestamps, IP addresses, error codes, and request paths from server logs for analysis or alerting.
Data Extraction — Use capture groups to extract specific data from structured text — like pulling URLs from HTML, quantities from invoices, or versions from changelogs.
String Replacement Patterns — Test your search pattern here before using it in a find-and-replace operation, sed command, or String.prototype.replace() call.
Learning Regex — Experiment with patterns and see results instantly. The visual highlighting makes it easy to understand how quantifiers, anchors, character classes, and groups work.
Tips for Power Users
- Use the g (global) flag to find all matches, not just the first one.
- The m (multiline) flag makes ^ and $ match the start/end of each line rather than the entire string.
- Named capture groups (?...) make your patterns more readable and the match table more informative.
- Lookaheads (?=...) and lookbehinds (?<=...) are supported in modern browsers for advanced matching.
- Test edge cases — try empty strings, strings with only whitespace, and strings with special Unicode characters to ensure your pattern is robust.
Why Use This Tool?
This regex tester runs entirely in your browser using JavaScript's native RegExp engine. Your test data never leaves your device, making it safe for testing patterns against sensitive log files, customer data, or proprietary content. It's faster than server-based testers and gives you the exact same behavior you'll get when the regex runs in your JavaScript application.