Cap'n Web is a new open source, JavaScript-native RPC protocol for use in browsers and web servers. It provides the expressive power of Cap'n Proto, but with no schemas and no boilerplate.

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Cap'n Web is a new open-source RPC protocol built in TypeScript that brings object-capability features to web development. Unlike traditional RPC systems, it requires no schemas or boilerplate, supports bidirectional calling, function passing by reference, and promise pipelining. The protocol works over HTTP, WebSocket, and postMessage, compresses to under 10kB, and enables complex interactions like authentication patterns and array operations in single network round trips. It aims to solve GraphQL's waterfall problem while maintaining familiar JavaScript programming patterns.

Cap'n Web: a new RPC system for browsers and web servers

Cap’n Web feels like the first time someone took RPC on the web seriously in 20 years.
No schemas, no generated boilerplate, just pure TypeScript objects moving across the network with promise pipelining and bidirectional references — it finally feels natural again.
The performance potential is real: chaining async operations without the GraphQL waterfall is a huge deal. But it’s not magic — you still need to think about security and resource budgets, because pipelining can just as easily amplify load if you’re careless.
Debugging remains the weak spot (tracing promises across the wire is tricky), yet the conceptual elegance outweighs it. If Cloudflare extends this with sturdy refs, better tooling, and integration with Workers’ new Node-HTTP layer, we might be looking at a genuine paradigm shift — the web growing up to speak objects instead of endpoints.
As someone who’s been around since CORBA and early SOAP days, this one finally feels like the right idea at the right time.

As someone who uses CF, would defiantly try that