Regex Tester
Test and debug regular expressions with real-time validation, syntax highlighting, and detailed match information.
Regex Tester – Test & Debug Regular Expressions Online
Use our free Regex Tester to instantly test, debug, and validate regular expressions online. This tool helps developers perfect their patterns with real-time matching, detailed group information, and syntax highlighting. See matches instantly as you type, with clear error messages and pattern explanations. Perfect for testing and debugging regex patterns.
Frequently Asked Questions
What is a Regex Tester?
A Regex Tester is a tool that helps you validate and debug regular expressions (regex patterns). It shows you exactly how your pattern matches text, highlights capture groups, and helps identify syntax errors. It's essential for developers working with pattern matching and text processing.
How do I test a regex online?
Simply enter your regex pattern in the pattern field and your test text in the input area. Our tool instantly shows all matches, capture groups, and any errors. You can also use flags like global (g), case-insensitive (i), and multiline (m) to modify how the pattern works.
Can I debug regex with this tool?
Yes! Our regex tester provides detailed debugging information including match positions, capture groups, and syntax validation. It highlights matches in your test text and shows a breakdown of each match, making it easy to understand how your pattern works.
What regex flavors does this support?
Our tester supports JavaScript's regex flavor by default, which is compatible with most modern programming languages. It includes support for all standard features like lookaheads, lookbehinds, capture groups, non-capturing groups, and Unicode patterns.
Regex Quick Reference
| Pattern | Description | Example |
|---|---|---|
^ | Start of line | ^hello |
$ | End of line | world$ |
. | Any character | h.t |
* | Zero or more | ab*c |
+ | One or more | ab+c |
? | Zero or one | ab?c |
{n} | Exactly n times | \d{3} |
{n,} | n or more times | \d{2,} |
{n,m} | Between n and m times | \d{2,4} |
Common Regex Patterns
| Description | Pattern |
|---|---|
[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,} | |
| URL | https?://[^\s/$.?#].[^\s]* |
| Phone (US) | \d{3}[-.]?\d{3}[-.]?\d{4} |
| Date (YYYY-MM-DD) | \d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12]\d|3[01]) |