WebAssembly Disassembler

How to convert WASM to WAT

1. Drop a .wasm file on the drop zone, or click it to choose one (up to 20 MB). You can also press Load an example module to see a small demo.
2. The tool checks the binary, validates it and shows the result: ✓ The module is valid., or the reason it is not.
3. Read the counters: Functions (imported and defined), Imports, Exports, Types, Memories, Tables and Globals.
4. Read the disassembly in WebAssembly text format (WAT), then Copy it or press Download .wat.
5. Adjust the output with the options: Use names from the name section, Folded expressions (S-expressions) and Inline exports.
6. Open the Sections, Imports and Exports tables for the layout of the file: each section with its byte offset, size and number of entries.

The module is never compiled, instantiated or run. The tool only reads its bytes and turns them into text, so it is safe to inspect a file you don’t trust.

What the WAT output shows

WebAssembly has two equivalent formats: the compact binary .wasm that browsers and runtimes load, and the text format .wat, which is meant for humans. The disassembler prints every part of the module in text form: function types, imports, function bodies, tables, memories, globals, exports, the start function, element segments and data segments.

By default, instructions are listed one per line in stack order, the way they are stored:

(func $add (param $a i32) (param $b i32) (result i32)
  local.get $a
  local.get $b
  i32.add)

With Folded expressions (S-expressions), operands are nested inside the instruction that uses them, as in (i32.add (local.get $a) (local.get $b)), which is often easier to follow. Inline exports writes (export "add") inside the function instead of in a separate list.

Names, debug information and validation

A .wasm file refers to everything by index. When the compiler kept a name custom section (common in debug builds), Use names from the name section shows the original names such as $factorial. Otherwise wabt generates names such as $f2 or $t0 so the text stays readable. Production builds are often stripped of names, so a minified module will show generated names only.

Validation follows the WebAssembly specification: types must match on the operand stack, indexes must exist, and so on. An invalid module is still disassembled when its structure can be read, with the validation error next to it, which helps when you debug a compiler or a hand-written binary. Post-MVP features such as SIMD, threads, bulk memory, reference types, multi-value, tail calls, exception handling, memory64 and garbage collection are enabled for reading.

This tool uses wabt.js, the JavaScript build of the WebAssembly Binary Toolkit (wasm2wat). It is loaded only when you open a file.