regex101: build, test, and debug regex
Regular expression tester with syntax highlighting, explanation, cheat sheet for PHP/PCRE, Python, GO, JavaScript, Java, C#/.NET, Rust.
Overview
Added
March 17, 2026
Subject & domain
computer-science-fundamentals · compiler-design
Grade range
Grade 9 (Freshman)–Grade 12 (Senior)
Page kind
Tool
Keywords
regexregex testerregular expressiondebuggerpcrephpgolangjavajavascriptpython.netc#rust
Introduction
Regex101 Overview
- Core Functionality: An online tool designed for building, testing, and debugging regular expressions.
- Key Features:
- Real-time syntax highlighting.
- Detailed explanations of regex patterns.
- Integrated cheat sheet for quick reference.
- Supported Languages:
- PHP (PCRE)
- Python
- Go
- JavaScript
- Java
- C#/.NET
- Rust
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