Cap'n Web is a JavaScript-native RPC system that supports object-capability patterns, bidirectional calling, and promise pipelining. Unlike traditional RPC systems, it requires no schemas or boilerplate, uses JSON serialization, and works across HTTP, WebSocket, and postMessage transports. The library enables passing functions and objects by reference, supports TypeScript integration, and includes advanced features like automatic resource management and cross-platform compatibility with Cloudflare Workers, Node.js, and browsers.