{
  "id": "magic/wasm",
  "family": "magic",
  "slug": "wasm",
  "title": "WebAssembly signature (00 61 73 6D)",
  "summary": "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).",
  "kind": "signature",
  "aliases": [
    "wasm magic",
    "\\0asm"
  ],
  "status": "standard",
  "verification": "verified",
  "tier": "B",
  "source_url": "https://webassembly.github.io/spec/core/binary/modules.html#binary-magic",
  "source_version": "WebAssembly Core Specification, Binary Format, Modules (magic + version)",
  "retrieved_date": "2026-05-29",
  "see_also": [
    "magic/elf"
  ],
  "ext_type": "file-signature@1",
  "ext": {
    "magic_hex": "00 61 73 6D",
    "offset": 0,
    "magic_ascii": "\\x00asm",
    "extensions": [
      "wasm"
    ],
    "mime": "application/wasm",
    "spec": "WebAssembly Core Specification, Binary Format",
    "notes": [
      "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."
    ]
  },
  "updated": "2026-05-29T00:00:00Z"
}