WebAssembly (WASM) modules have no conception of the filesystem, the network, or much else outside the browser sandbox. Many are experimenting with using the format outside the browser for server-side applications. How can it be used both serverside and clientside?

WASI is the WebAssembly System Interface. It was designed to make WebAssembly modules easy to use in non-browser environments. Its scope includes

• APIs for host filesystems, network stacks, and other resources.
• APIs for graphics, audio, input devices
• APIs for encryption, format conversion, and other transformations (particularly where hardware acceleration may be available on some platforms)

Can WASM/WASI serve two masters: web-first and server-first?

Adding WASI to the WebAssembly target creates some problems:

• Larger binary sizes for unnecessary features (when the module runs in the browser)
• Concepts that don't map cleanly to the browser sandbox
• Overlap with existing Web APIs

Can it be done in a way that doesn't fragment the toolchain, developers, and userbase? Will WASI targets be as portable? Is it a technology problem or a standards problem?