WAT to WASM Converter & Formatter — Free Online

Working with the WebAssembly Text Format

What is WAT?

WAT (WebAssembly Text Format, sometimes .wast) is the human-readable representation of a wasm module — S-expressions like (func (result i32) (i32.const 42)). Tools emit it for debugging, and it's the format you edit by hand when hand-crafting or patching modules.

The binary format (.wasm) is what actually runs; WAT and wasm convert into each other losslessly for valid modules.

What each button does

• Format — parses the WAT and reprints it with canonical indentation. Handy after hand-editing or pasting minified text.
• Minify — collapses whitespace and strips comments for the smallest possible source.
• Compile — assembles the WAT into a .wasm binary you can download and run anywhere.
• Drop a .wasm — decompiles it to WAT with names from the name section applied, so functions read $add instead of $f12.

Supported features

The parser accepts the full spec plus the common post-MVP features: bulk memory, sign extension, multi-value, reference types, SIMD, threads, mutable globals, and exception handling. That covers output from rustc, AssemblyScript, and most other compilers.