Validating an email or phone number pattern
Validation patterns need to handle many edge cases. Testing against a variety of valid and invalid inputs helps you find false positives and negatives before deployment.
Regex Tester
Test regular expressions with real - time highlighting. See matches, capture groups, and flags instantly. Supports JavaScript regex syntax.
Debugging regular expressions in a code editor means running and re - running your program to see what matches. An interactive regex tester highlights matches in real time and shows capture groups instantly, so you can iterate faster.
How to use
- Enter your regular expression pattern
- Choose flags (global, case - insensitive, multiline, etc.)
- Paste or type your test string
- See matches highlighted in real time with group details
Why this tool is useful
Regular expressions are powerful but notoriously difficult to write and debug. A single character change can completely alter what a pattern matches. Testing a regex against sample strings interactively is far more productive than running scripts repeatedly.
A regex tester shows matches, capture groups, and failures in real time, helping you refine patterns before embedding them in code.
What this tool helps with
Instant feedback on matches and groups reduces debugging time significantly. You can test edge cases and unexpected inputs alongside your expected matches to build more robust patterns.
Seeing capture groups highlighted makes it easier to verify that your extraction logic works correctly before you integrate the regex into application code.
Examples
Extracting data from log lines using capture groups
Log parsing often requires precise group extraction. A tester highlights which parts of each line match each group, making it easier to confirm your pattern is correct.
Debugging a pattern that matches too broadly or too narrowly
Regex issues are often subtle, matching unexpected strings or missing valid ones. Testing incrementally against sample data helps you isolate which part of the pattern needs adjustment.
Recommended for
Recommended for developers writing validation logic, anyone parsing structured text, and teams that maintain regex patterns for routing, filtering, or data extraction.
Privacy and processing
All matching happens in your browser. No data is sent to our servers.
Frequently Asked Questions
What regex syntax is supported?
This tool uses JavaScript's built - in RegExp engine, supporting all standard JS regex features including lookahead, lookbehind, named groups, and Unicode.
What are regex flags?
Flags modify how the pattern matches: g (global - find all matches), i (case - insensitive), m (multiline - ^ and $ match line boundaries), s (dotAll - . matches newlines).
Can I see capture groups?
Yes, all captured groups (including named groups) are displayed for each match with their index and value.
Why is my regex showing an error?
The tool shows a real - time error if your pattern has invalid syntax. Check for unmatched parentheses, brackets, or invalid escape sequences.
Does this support lookbehind?
Yes, JavaScript supports both positive (?<=...) and negative (?<!...) lookbehind assertions in modern browsers.
Is my test data private?
Yes. All matching runs locally in your browser. No data is sent to any server.
Can I use this for other languages?
Regex syntax is largely similar across languages. However, some features (like lookbehind) may differ. This tool uses JavaScript syntax specifically.
Does this work offline?
Yes, once loaded, the tester works entirely in your browser without needing an internet connection.
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