express-sed

Express middleware for transforming HTTP response bodies using string replacements, regex, or sed-like transform definitions. Current stable version is 1.1.3, released with a low cadence. It works with Express 4 and 5, ships TypeScript types, and requires Node.js >= 20. Unlike general interceptors, it provides a simple sed-like syntax for content rewriting, focused on string substitution without buffering entire responses (streaming compatible). Supports both function-based replacements and a compact sed transform definition with content type filtering.