Regex Tester

Debugged Regular Expressions Before Shipping

Regular expressions are powerful but cryptic. A single typo in a pattern—a missing escape, wrong quantifier, or inverted character class—breaks validation, parsing, or data extraction. Testing regex in a REPL or code editor is slow: write, run, debug, repeat. By the time you notice a problem in production, it's already matched the wrong things or missed valid data.

This interactive Regex Tester shows you exactly what your pattern matches, with live highlighting and instant feedback. Type a pattern, test it against sample strings, see every match highlighted. If it's not working, adjust and see the results immediately. No deploy cycle, no guessing.

See Matches in Real Time

As you type your regex pattern, matches are highlighted in the test string instantly. You see:

• Highlighted Matches: Each match is colored and numbered so you can count them and spot which parts of the string are matched
• Captured Groups: If your pattern includes capture groups (...), see exactly what each group captures
• Match Count: Total number of matches found
• Detailed Group Information: See the content and position of each captured group

This visual feedback makes regex bugs obvious. If your pattern is matching too much or too little, you see it immediately.

Match and Replace Modes

Match Tab: Test your pattern to ensure it finds the right strings. Verify emails, URLs, phone numbers, dates, or any text pattern you need to extract or validate.

Replace Tab: Enter a replacement string and see the result instantly. Use capture group references ($1, $2) to reorganize matched content. This is invaluable for refactoring data, renaming patterns, or transforming strings without writing temporary code.

Full JavaScript Regex Flags

Control how the pattern behaves:

• Global (g): Find all matches, not just the first
• Case-Insensitive (i): Match regardless of uppercase/lowercase
• Multiline (m): ^ and $ match line boundaries, not just string boundaries
• DotAll (s): . matches newlines

Useful Sample Patterns Included

Stuck? Quick samples include patterns for:

• Email addresses
• URLs and web links
• Dates and times
• Phone numbers
• Alphanumeric validation

Select a sample, see it in action, then modify for your specific needs.

Real Development Use Cases

Form Validation: Test email, password, phone number, and other input patterns before embedding them in forms.

Data Parsing: Extract fields from logs, CSV data, or unstructured text. Test your extraction pattern to ensure you're getting the right content.

String Transformations: Rename variables in code, reformat dates, or restructure text using replacement patterns with capture groups.

Find & Replace Workflows: Test complex find-and-replace operations on entire files without risking mistakes.

Debugging Pattern Issues: When code using regex isn't working correctly, isolate the pattern here and test it in isolation.

100% Local, No External Processing

Patterns stay in your browser. Test sensitive data or internal formats without any concern about privacy.