wire / magic / wasm

WebAssembly signature (00 61 73 6D)

A WebAssembly binary module begins with the 4-byte magic 0x00 'a' 's' 'm' (\0asm), immediately followed by a 4-byte little-endian version number (currently 0x01 0x00 0x00 0x00).

magic kind signature status standard verification verified tier B file-signature@1

aka: wasm magic · \0asm

file signature

magic: 00 61 73 6D @ offset 0

ascii: \x00asm

.wasm application/wasm

spec: WebAssembly Core Specification, Binary Format

Magic = 00 61 73 6D ('\0asm').
Immediately followed by the 4-byte version, little-endian: 01 00 00 00 for version 1.
So a typical module starts 00 61 73 6D 01 00 00 00, then a sequence of sections.

provenance

source: https://webassembly.github.io/spec/core/binary/modules.html#binary-magic
version: WebAssembly Core Specification, Binary Format, Modules (magic + version)
retrieved: 2026-05-29 · updated: 2026-05-29T00:00:00Z

WebAssembly signature (00 61 73 6D)

file signature

provenance

see also