web dev//runtime

A runtime is the environment where code executes, providing the available APIs, the memory limits, the event loop and the execution model.

A runtime is the environment where code executes, providing the available APIs, the memory limits, the event loop and the execution model.

The engine and the runtime are different layers. V8 is a JavaScript engine that compiles JS to machine code. Node.js is a runtime that uses V8 and adds system APIs (filesystem, networking, crypto), while Workers is another runtime on V8 that adds Cloudflare APIs (D1, R2, KV) without a filesystem or full Node.js. The same engine thus sits under runtimes with different APIs.