WASM File Viewer — Inspect WebAssembly Binaries Online

Reading a WebAssembly binary

The anatomy of a .wasm file

A wasm module is a sequence of sections after an 8-byte header (the \0asm magic and a version number): type signatures, imports, function declarations, tables, memories, globals, exports, element segments, function bodies (code), and data segments. Each section is identified by a numeric ID and a byte length — this tool lists them all with their sizes, which is the fastest way to see where a module's bytes are going.

Custom sections (ID 0) carry metadata; the most common is the name section, which maps function indexes to readable names.

When this is useful

• Checking what a module imports (which host functions it expects) and what it exports
• Seeing whether a build includes debug names or unexpected custom sections
• Estimating where size comes from (code vs data sections) before optimizing
• Verifying that a downloaded module is actually a wasm binary at all

Related tools

To go further, use our WAT ⇄ WASM converter to decompile the binary to the readable text format, edit it, and compile it back.