> WASI stands for WebAssembly System Interface. It's an API designed by the Wasmtime project that provides access to several operating-system-like features, including files and filesystems, Berkeley sockets, clocks, and random numbers, that we'll be proposing for standardization.

Read more here - https://github.com/bytecodealliance/wasmtime/blob/main/docs/...

Am not expert, but here's the understanding I've picked up:

When you use JavaScript through Node, your JS gets the ability to open files and make network sockets and so on, because there are a set of APIs implemented by Node and exposed to your JS code, like so:

JS <-> native APIs <-> Node implementation of platform-specific operations

WASI applies to WebAssembly instead of JS. So again if we're on Node:

wasm <-> native APIs (WASI) <-> Node implementation of platform-specific operations

But WASI is much more general than Node's APIs, and meant to be used by different engines in different environments (browsers, native bindings, etc).

Simplely, it's wasm's POSIX

API for Webassembly. Common interface.