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Regex Tester

Test and debug regular expressions instantly. Free, no signup required.

Regular expressions (regex) are patterns used to match, search, and manipulate text in programming. They are used in form validation (checking if an email address is correctly formatted), log file analysis (extracting specific entries), data cleaning (removing unwanted characters), and search and replace operations in text editors and code. Writing a regex that works exactly as intended often requires iteration — this tester lets you write a pattern and immediately see which parts of your test string it matches, highlighted in yellow. Common pre-built patterns for email, URL, phone, IP address, and date are available as quick-start options.

COMMON PATTERNS

//g

How to use

  • • Enter a regex pattern or pick a common one above
  • • Toggle flags as needed (g = global, i = case insensitive)
  • • Paste your test string — matches highlight instantly

Frequently Asked Questions

What regex syntax does this tester support?

JavaScript regex syntax is used. This supports most standard regex patterns including character classes, quantifiers, groups, lookaheads and lookbehinds.

What do the flags mean?

g means global (find all matches), i means case-insensitive, m means multiline (^ and $ match line starts/ends), s means dot matches newlines.

Why are my matches highlighted in yellow?

Yellow highlighting shows each match found in the test string. This makes it easy to visually verify your pattern is matching the right text.

Can I test common patterns like email or URL?

Yes. Use the preset buttons at the top to load common patterns for email, URL, phone number, IP address, date and hex colour.

Why does my regex show an error?

An error means the regex syntax is invalid. Check for unclosed brackets, invalid escape sequences or unsupported features.