Regex Tester
Test regex patterns and view match results.
Data is never sent to the server. Everything runs locally in your browser. Safe for sensitive information.
About this tool
This tool tests regex patterns in real time. Three features: 1) Enter pattern and test text for instant match results, 2) Supports g (global), i (ignore), m (multiline) flags, 3) All processing in browser—no data sent to server. Ideal for validation pattern verification.
Does the regex you wrote really catch only the characters you intended? When writing validation or extraction logic, building a perfect pattern on the first try is extremely hard. Before an unexpected match turns into a bug, test it with this tool. Enter a pattern and target text, and the matching parts are highlighted right away. It works without server communication, so you can safely paste actual customer data or logs for testing.
Tool interface
Usage
- Enter regex pattern and test text
- Select g (global), i (ignore), m (multiline) flags
- Match results and indices are displayed in real time
When to use
Verifying regex behavior, testing validation patterns, checking extraction patterns for logs.
Examples
[a-z]+ for lowercase, \d{4}-\d{2}-\d{2} for date, ^[\w.-]+@[\w.-]+\.\w+$ for email.
FAQ
What is regex?
Pattern notation for strings. Used for validation, search/replace, log extraction.
What is the g flag in regex?
Global—match all occurrences, not just the first. Without g, only first match is returned.
Regex for email validation?
Simple: ^[\w.-]+@[\w.-]+\.\w+$. Full validation is complex; prefer a library for production.
What does \d mean in regex?
One digit (0-9). \d{4} = 4 digits, \d+ = one or more digits.
How to use the regex tester tool?
Enter a pattern and test text. Match results are shown in real time. The g, i, and m flags are supported.
What is the i flag in regex?
Makes matching case-insensitive. /[a-z]/i matches both A and Z. Select the flag in this tool to test.
What is the m flag in regex?
Multiline mode. ^ and $ match at the start and end of each line. Useful for searching text with newlines.
Does the regex tester send my data?
No. Everything runs in your browser. Patterns and text are never sent to a server.
What does .* mean in regex?
Any character (except newlines) repeated 0 or more times. .*? is non-greedy and matches as little as possible.
How do I validate a regex pattern?
Check the matches against test text with this tool to prevent unexpected or missed matches.
Is Regex Tester free?
Free to use, no sign-up required.
Is data sent to a server?
Input is processed locally in your browser—nothing is sent to our servers.
Supported browsers?
Tested on recent Chrome, Edge, Firefox, and Safari.
Offline use?
Core features work offline after the first load.
vs CLI or desktop apps?
Regex Tester is an install-free online alternative to CLI or desktop apps.
When to use it?
Use it when: Verifying regex behavior, testing validation patterns, checking extraction patterns for logs.
Usage example?
Example: [a-z]+ for lowercase, \d{4}-\d{2}-\d{2} for date, ^[\w.-]+@[\w.-]+\.\w+$ for email.
Main features?
Real-time match results, g/i/m flags, Match indices display
How is this different from similar tools?
Regex Tester runs in the browser with no install—ideal for quick checks before heavier CLI or IDE workflows.
Search keywords
regex tester, regex test online, regular expression tester, regex validator, regex matcher, regex checker
Basic workflow
- Enter regex pattern and test text
- Select g (global), i (ignore), m (multiline) flags
- Match results and indices are displayed in real time
Practical use cases
- Verifying regex behavior, testing validation patterns, checking extraction patterns for logs.
- This tool tests regex patterns in real time. Three features: 1) Enter pattern and test text for instant match results, 2) Supports g (global), i (ignore), m (multiline) flags, 3) All processing in browser—no data sent to server. Ideal for validation pattern verification.
- Real-time match results
- g/i/m flags
Privacy & data handling
Input is processed locally in your browser—nothing is sent to our servers.
Things to watch out for
- Treat Regex Tester as a quick check — re-verify critical values in your editor or CI before shipping.
- This tool runs locally: closing the tab clears unsaved input. Copy results you need to keep.
- Very large pastes can freeze a tab briefly — wait for the result before closing the tab.