Regex Tester
What is Regex Tester? (Quick Answer)
Test regular expressions online Free online tool, no registration required, 100% client-side processing.
Test regular expressions online
By Craftisle Team
About Regex Tester — Free Online Tool
How to Use Regex Tester — Step by Step
- Enter a regex pattern
Type your regular expression pattern (e.g., ^[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,}$).
- Add test string
Paste or type the text you want to test against.
- View matches
Matching portions are highlighted. Match groups are displayed below.
- Test replace
Optionally enter a replacement string to preview the result of regex replace.
Use Cases for Regex Tester
Form validation
Test email, phone, and password validation regex patterns before deploying.
Data extraction
Build regex patterns to extract URLs, dates, or structured data from text.
Log analysis
Create regex patterns to parse and filter server log files.
FAQ — Regex Tester Free Online Tool
Which regex flavor is used?
By default, JavaScript regex (ECMAScript). You can switch to Python or PCRE mode for advanced features like lookbehind.
What does the 'g' flag do?
The 'g' (global) flag finds ALL matches, not just the first one.
Why is my regex not matching?
Common issues: forgetting to escape special chars (., *, +), or using greedy quantifiers (*) when you want lazy (*?). Check the flags too.