Maybe this is more of a info than a bugreport because it's already common knowledge but i couldn't find any info about the constraints of the released file and hope it might help someone?

I'm on Windows and couldn't get a language compiled with emscripten to work together with the tree-sitter.js and tree-sitter.wasm files from the latest GitHub release as described here with some basic test code:

const Parser = require('web-tree-sitter');
Parser.init().then(() => {
    (async function(a, b) {
        const language = await Parser.Language.load('tree-sitter-g_code_sinumerik.wasm');
        const parser = new Parser;

I always got the error

Assertion failed: undefined
node_modules/web-tree-sitter/tree-sitter.js:1
Uncaught RuntimeError: abort(Assertion failed: undefined). Build with -s ASSERTIONS=1 for more info.

Turns out this is because the emcc i'm using

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.0 (8e1e305519e1027726a48861a1fec5662f7e18a2)

is too new or because i'm on windows?

When i compare a wasm i get through npm install, f.e. tree-sitter-javascript.wasm with my own, there's a difference in the dylink secion.
The former is at

wasm-objdump -h tree-sitter-javascript.wasm
tree-sitter-javascript.wasm:    file format wasm 0x1
Sections:
   Custom start=0x0000000a end=0x00000018 (size=0x0000000e) "dylink"

and mine at
Custom start=0x0000000e end=0x0000001e (size=0x00000010) "dylink.0"

After rebuilding tree-sitter.js and tree-sitter.wasm the error disappeared because the checks done in loadModule (they look like these here at line 370 ff) now match the expectations.