What is Webassembly?

Part : Specification

Part: 0 1 2


The spec consists of three parts

1. Core - which is most of it 2. Javascript - which is specific to JS 3. Web - which is the smalles part of all



The core spec is very long and detailed.

The text representation of WASM is in terms of s-expressions.



All the stuff about what wasm and js can share and how they should share it - memory, tables, namespaces. All good stuff, but a bit over my head at the moment, except to know that it's there (and, I think it's useful to have an idea about what isn't in there.


  • The streaming compilation and instantiation methods.

Use the fetch API (which I need to add to the list)

you have to set the type as application/wasm

same-origin is enforced

format of error messages

A WebAssembly location is a reference to a particular instruction in the binary, and may be displayed by a browser or engine in similar contexts as JavaScript source locations. It has the following format:



${url} is the URL associated with the module, if applicable (see notes).

${funcIndex} is the function index relative to the module.

${pcOffset} is the offset in the module binary of the first byte of the instruction, printed in hexadecimal with lower-case digits, with a leading 0x prefix.