Regex Tester

Overview

Regex Tester is an interactive environment for writing and testing regular expressions. Enter a pattern and test strings to see matches highlighted in real time. An AI explanation mode describes what a given regex does in plain English.

Writing a Regex

1. Enter your regular expression in the Pattern field at the top.
2. Select flags from the flag buttons: g (global), i (case-insensitive), m (multiline), s (dotAll), u (unicode).
3. In the Test String panel, enter the text to test against.
4. Matches are highlighted immediately in yellow.

Match Details

The Matches panel shows:

• Total match count
• Each match with its start and end index
• Captured groups (groups 1, 2, 3, …) listed separately
• Named capture groups displayed by name

AI Explanation

Click Explain Regex to get an AI-generated plain-English description of what the pattern does.

Common Patterns Library

Click Library to browse pre-built regex patterns for common use cases:

• Email address validation
• URL matching (http/https, optional path and query)
• Phone numbers (multiple country formats)
• IP addresses (IPv4 and IPv6)
• Date formats (ISO 8601, US, EU)
• Password strength rules