Back to Tools
Regex Tester
Regex Interactive Hub
Advanced testing, substitution, code generation, and real-time pattern analysis
INTERACTIVE PRO
/
/
Visual Match Highlighting
Detailed Matches
Pattern Explanation
Implementation Code Generator
JavaScript
PHP
Python
Java
About the Regex Tester
Test regular expressions against sample text, see every match and capture group highlighted, and try replacements before using the pattern in your code.
How to use the Regex Tester
- Enter your Regular Expression Pattern and the Flags (for example g, i, m).
- Enter the text to test. Use Sample to load an example.
- Press Test Regex to see matches, groups and timing. Add a Substitution to preview a replace.
| Token | Meaning |
|---|---|
| \d | A digit (0 to 9) |
| \w | A letter, digit or underscore |
| \s | A whitespace character |
| . | Any character except a new line |
| ^ and $ | Start and end of the text (or line with m) |
| + * ? | One or more, zero or more, optional |
| (...) | A capture group |
| [a-z] | One character from a range |
When to use the Regex Tester
- Building and debugging a regular expression against sample text.
- Validating formats such as emails, dates and phone numbers.
- Finding and replacing patterns in a large block of text.
Common mistakes to avoid
- Forgetting to escape special characters such as ., ?, + and (.
- Being too greedy. .* can match far more than you intend; try .*? instead.
- Testing only on matching text. Try examples that should not match too.
Tips
- Flags: g finds all matches, i ignores case and m makes ^ and $ work per line.
- Very complex patterns with nested repetition can be slow. Keep patterns as specific as possible.
Frequently Asked Questions
The tester uses the JavaScript regular expression engine in your browser, which is very close to most other languages but not identical.
g finds all matches, i ignores case and m lets ^ and $ match at each line.
Regex flavours differ slightly between languages. Check the syntax for the language you use.