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Regex Tester & Builder

Live highlighting · flag toggles · cheat sheet

//g
Flags:0 matches
Common Patterns
Match Highlights
Hello World! My email is john.doe@example.com or jane@test.org. Visit us at https://www.example.com or http://test.io for more info. Call us: (555) 123-4567 or 800.555.0199. IP address: 192.168.1.1 | Color: #FF5733 and #abc. Date: 2024-01-15 | ZIP: 90210-1234 | Username: john_doe99
Regex Cheat Sheet
Character Classes
Anchors
Quantifiers
Groups & Lookaround

💡 Tip

Click any token above to append it to your pattern. Use the Common Patterns buttons to load ready-made expressions.

Best Online Regex Tester & Debugger - Everything You Need to Know

A regular expression (regex or regexp) is a sequence of characters that defines a search pattern. They are used in programming languages, text editors, and command-line tools to find, validate, extract, and replace text. From validating email addresses to parsing log files, regex is an indispensable tool in every developer's toolkit.

How to Use This Tool

  1. Type or paste your regular expression in the Regular Expression input field.
  2. Adjust the regex flags (g, i, m, s) according to your needs.
  3. Type or paste your test string in the Test String area to inspect real-time matches.
  4. Use the Cheat Sheet on the right to build expressions, or click any token to append it.

Frequently Asked Questions (FAQ)

Q: How do regex flags change behavior?

A: Flags modify the search behavior: 'g' finds all matches instead of stopping after the first, 'i' ignore cases, 'm' enables multiline anchors (^ and $), and 's' allows dot (.) to match newlines.

Q: Is my test data safe?

A: Yes. All regex compilation and matching are processed locally in your browser using JavaScript's native RegExp object. No text is sent to a server.