WebAssembly Documentation

What WebAssembly is, why it exists, where it fits, and when not to use it.

Validation, compilation, instantiation, interpreter/baseline/JIT paths, and why predictable types matter.

How WebAssembly differs from Flash, ActionScript, Shockwave, and NPAPI plugin models.

Source languages, compiler frontends, IRs, backends, WAT, binaries, imports, and glue.

Magic bytes, version, sections, opcodes, LEB128, and byte-level inspection.

Code signing, SRI, hashes, trusted origins, and what browsers actually validate.

How to load WASM from fetch, streaming APIs, ArrayBuffer, Uint8Array, Blob, upload, or generated bytes.

Pages, growth, typed array views, JS sharing, strings, pointers, bounds checks, and W^X safety.

Interpreters, self-hosting, bytecode in memory, host compilation, and why this is not raw memory execution.

funcref, externref, call_indirect, virtual tables, imported/exported tables, and safety.

The difference between compiled module code and running instance state.

Mutable/immutable globals, JS Global objects, numeric globals, imported string constants, and string passing.

Inspect memory, tables, globals, exports, mutate state, call functions, and observe traps.

Loading WebAssembly modules with module-like semantics and feature-detected demos.

Canvas, WebGL, WebGPU, DOM, BOM, audio, camera, files, workers, service workers, and WASI.

Why generated JS glue exists and how C/C++ libraries map onto web APIs.

Text format, nested and flat forms, Lisp-like syntax, binary mapping, and why WAT is useful.

Operand stack, value types, blocks, loops, branches, calls, and stack effects.

Names, indices, params, results, locals, local.get/set/tee, exports, and imports.

Reusable signatures, type indices, params/results, typed references, and proposal support.

Direct calls, indirect calls, imported callbacks, JavaScript exports, dispatch tables, and globals.

Importing functions, memory, tables, globals, host functions, and env namespaces.

Declaring/importing/exporting memory, loads/stores, data, fill/copy/init/drop, memory64, and custom page warnings.

WebAssembly.Memory, ArrayBuffer, SharedArrayBuffer, typed views, imported/exported memory, and shared state.

State machines, pure functions, data flow, compiler IR, deterministic execution, and runtime state.

UTF-8, TextEncoder/TextDecoder, pointer/length passing, and a base64 decoder scaffold with altchars.

Shared memory, SharedArrayBuffer, workers, shared workers, headers, notifications, and browser support.

WebAssembly is a namespace with static methods and constructor interfaces, not a class to instantiate.

Compiled module representation, imports, exports, storage, caching, and sharing.

Mutable/immutable globals, JS-created globals, imports, exports, and numeric limitations.

Instance creation, exports, imports, running state, calls, and inspection.

Create, read, write, grow, share, and use memory without a WASM module.

Tables, funcref, externref, get/set/grow, and dispatch safety.

Exception/tag interfaces, thrown errors, tag data, retries, and support caveats.

CompileError, LinkError, RuntimeError, validation errors, import errors, memory errors, traps, and type mismatches.

What opcodes are, how WAT maps to binary bytes, prefixed opcode spaces, LEB128 immediates, and why some WAT forms have no opcode.