Regex Checker Tool
Test regular expressions in real-time with match highlighting, explanations, and a pattern library.
Regular Expression
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Test String
Match Result
Enter a test string to see matches
Replace
Replace Preview
Explanation
Common Regex Patterns
How to Use
1
Enter Regex
Enter a regular expression pattern. Toggle flags (g, i, m, s, u) as needed.
2
Enter Test String
Enter a test string to see matches highlighted in real-time.
3
View Results
Check the match details table for group captures and positions. Use the Replace tab to preview replacements.
4
Use Pattern Library
Insert common regex patterns with one click from the pattern library.
About Regex Checker
A web tool to test regular expressions in real-time using JavaScript's regex engine. All processing happens in your browser. Your text is never sent to any server.
Features
- Real-time MatchingSee matches highlighted instantly as you type. Debug regex efficiently.
- Explanation PanelEach token is explained clearly. Great for learning regex.
- Pattern Library (25+)Insert common patterns for email, phone, URL, date, and more with one click.
- Privacy ProtectedAll processing happens in your browser. Text is never sent to servers.
Use Cases
- Test input validation regex (email, phone, postal code)
- Test log file pattern extraction
- Verify Google Analytics filter patterns
- Create search & replace patterns for text editors
- Learn and understand regex syntax
FAQ
Is the regex checker free to use?
Yes, completely free. No registration required.
Which regex engine is used?
It uses JavaScript's regex engine (ECMAScript). Some syntax may differ from PHP (PCRE) or Python (re).
Is my text saved anywhere?
No, your text is never sent to or stored on any server. All processing is local.
Can I test regex with Japanese text?
Yes, Japanese text is fully supported. Enable the Unicode flag (u) for proper surrogate pair handling.
Can I use the patterns from the library in my code?
The patterns are common examples. Adjust them to your specific requirements.
Why does my regex show "No match"?
Common causes: 1) Missing flags (use i for case-insensitive), 2) Anchor misuse (^ and $ without m flag), 3) Missing escapes for special characters.
How do $1 and $2 work in replacement?
$1 refers to the 1st capture group, $2 to the 2nd, etc. Named groups use $<name>.
Can I use it on my smartphone?
Yes, it works on all devices including smartphones, tablets, and PCs.
How does this compare to regex101?
regex101 supports multiple engines for advanced users. This tool focuses on usability with an explanation panel and pattern library.
What are the differences between JavaScript and PHP regex?
Key differences: 1) PHP PCRE supports recursive patterns and atomic groups, JS does not. 2) Lookbehind support varies. 3) Named capture syntax differs slightly.