Regex Playground MCP Server

Interactive regex tester with match highlighting, capture group visualization, and pattern explanation.

Features

• Real-time Regex Testing - Test patterns against strings with instant feedback
• Match Highlighting - See all matches with their exact positions and indices
• Capture Group Visualization - View named and numbered capture groups separately
• Pattern Explanation - Break down regex patterns into individual tokens with descriptions
• Flag Support - Test with various flags (global, case-insensitive, multiline, dotAll, unicode)
• Error Handling - Clear error messages for invalid regex patterns

Installation

npm install @gongrzhe/server-regex-playground

Usage

As a CLI

npx @gongrzhe/server-regex-playground

Claude Desktop Configuration

{
  "mcpServers": {
    "regex-playground": {
      "command": "npx",
      "args": ["-y", "@gongrzhe/server-regex-playground"]
    }
  }
}

Claude Code Configuration

claude mcp add regex-playground -- npx -y @gongrzhe/server-regex-playground

Tools

test-regex

Tests a regular expression against a string and returns all matches with indices and capture groups.

Inputs:

• pattern (string): The regex pattern to test
• testString (string): The string to test the regex against
• flags (string, optional): Regex flags (g, i, m, s, u)

Output:

• matches (array): Array of match objects with fullMatch, index, length, and capture groups
• matchCount (number): Total number of matches found
• isValid (boolean): Whether the pattern is valid
• error (string, optional): Error message if pattern is invalid

explain-regex

Breaks down a regular expression into tokens and explains each part.

Inputs:

• pattern (string): The regex pattern to explain
• flags (string, optional): Regex flags (g, i, m, s, u)

Output:

• tokens (array): Array of token objects with token, description, and position
• summary (string): High-level summary of the pattern and flags
• isValid (boolean): Whether the pattern is valid
• error (string, optional): Error message if pattern is invalid

Example Prompt

Test the regex (\d{4})-(\d{2})-(\d{2}) against "Today is 2026-02-14 and tomorrow is 2026-02-15"

Then explain what each part of the pattern means.

License

MIT