Regex Tester

Regular expressions are powerful but easy to get wrong. This tester highlights every match as you type, lists capture groups and their positions, and previews search-and-replace results, so you can build and debug patterns for validation, parsing and text clean-up with confidence.

Common uses

• Build validation patterns for emails, phone numbers, postcodes and IDs.
• Extract data such as dates, prices or URLs from logs and documents.
• Test find-and-replace patterns before using them in VS Code, Sublime or a script.
• Learn regex step by step with the built-in cheat sheet.

Tips for best results

• Start simple and add complexity one piece at a time.
• Use ^ and $ with the m flag to match whole lines.
• Escape special characters such as . ? + * ( ) [ ] with a backslash when you mean them literally.
• Prefer specific character classes such as [^,]+ over .* to avoid matching too much.

Flags explained

g finds all matches instead of only the first, i ignores case, m makes ^ and $ match at line breaks, s lets . match newlines, u enables full Unicode support including \p{…} classes, and y (sticky) matches only at the current position. The tester always searches globally for highlighting, but respects your flags for the replace preview.

Validating international data

Real-world data is global. Names include accents and non-Latin scripts, postcodes vary from 3 to 10 characters, and phone numbers have many formats. Use \p{L} for letters in any language, avoid overly strict patterns for names and addresses, and for phone numbers consider the international E.164 format: a plus sign followed by up to 15 digits.