RegexExplain

Visualize and debug regular expressions with step-by-step match tracing

Code & DevelopmentFree

RegexExplain renders regular expressions as visual railroad diagrams and provides step-by-step match tracing showing exactly how the regex engine processes each character of the input string. The tool highlights backtracking behavior, identifies catastrophic backtracking patterns that could cause ReDoS vulnerabilities, and suggests optimized alternatives. It supports PCRE, JavaScript, Python, and Go regex flavors with flavor-specific behavior differences clearly annotated. Developers use it to understand and debug complex regex patterns they inherited or generated.

Key Features

• ✓Railroad diagram visualization
• ✓Step-by-step match tracing
• ✓Catastrophic backtracking detection
• ✓Multi-flavor support
• ✓ReDoS vulnerability warnings