path-to-regexp is a TypeScript library that converts path patterns like '/user/:id' into regular expressions for URL matching. It provides a suite of functions: parse, compile, match, stringify, and pathToRegexp. The library handles named parameters, wildcards, optional groups (using braces), custom delimiters, and complex backtracking scenarios. It is the foundation for Express-style routing but is framework-agnostic. The code is well-structured, thoroughly tested (including ReDoS safety checks), and follows modern TypeScript practices. It is a mature, high-quality library with active maintenance.