Learn Wat - 10 Code Examples & CST Typing Practice Test
WAT (WebAssembly Text Format) is the human-readable, assembly-like syntax used to represent WebAssembly binaries. It allows developers to write, inspect, debug, and understand Wasm modules using a clear, text-based format before compiling to .wasm.
Learn WAT with Real Code Examples
Updated Nov 25, 2025
Explain
WAT provides a low-level, readable, LISP-like syntax for WebAssembly modules.
It directly maps to the binary WebAssembly format, instruction-by-instruction.
Used primarily for debugging, hand-crafted Wasm, education, and minimal runtime experimentation.
Supports fine-grained control over Wasm memory, functions, imports, exports, and types.
Typically compiled into Wasm using wat2wasm tools or integrated toolchains.
Core Features
Module definitions using `(module ...)`
Functions with explicit param/returns
Linear memory definition and access
Imports and exports
Instructions for control flow, arithmetic, memory, tables
Basic Concepts Overview
Stack machine - operations push/pop values
Linear memory - explicit memory access
S-expressions - LISP-like syntax
Instructions - Wasm opcodes in text form
Module structure - imports, exports, functions, types
Project Structure
module.wat - main Wasm text module
module.wasm - compiled binary
index.js - loader/interop script
tests/ - validate Wasm output
examples/ - sample WAT modules
Building Workflow
Write .wat module
Compile using wat2wasm
Inspect binary via wasm2wat
Load in browser or Node.js
Call exported functions from JS
Difficulty Use Cases
Beginner: simple add function
Intermediate: memory access + loops
Advanced: tables, imports & exports
Expert: manual stack manipulation + complex control flow
Auditor: analyze binary from wasm2wat
Comparisons
WAT vs Wasm Binary: WAT is readable; binary is compact and executable
WAT vs Rust-Wasm: WAT is manual; Rust generates Wasm automatically
WAT vs AssemblyScript: WAT is low-level; AS is high-level TS-like
WAT vs C/C++-Wasm: WAT is hand-crafted; C compiles high-level code
WAT vs Go/TinyGo: WAT avoids runtimes entirely
Versioning Timeline
2015 - WebAssembly concept announced
2017 - WebAssembly MVP in browsers
2018 - WAT standardized as text format
2022 - WAT gains support for GC, reference types
2024-2025 - Memory64, tail calls, component model support
Glossary
WAT - WebAssembly Text Format
S-expression - LISP-like syntax
Stack machine - push/pop architecture
WASI - WebAssembly System Interface
Opcode - low-level instruction
Frequently Asked Questions about Wat
What is Wat?
WAT (WebAssembly Text Format) is the human-readable, assembly-like syntax used to represent WebAssembly binaries. It allows developers to write, inspect, debug, and understand Wasm modules using a clear, text-based format before compiling to .wasm.
What are the primary use cases for Wat?
Learning WebAssembly internals. Debugging or inspecting Wasm modules. Creating tiny hand-crafted Wasm binaries. Reverse engineering WebAssembly. Testing Wasm instructions or host bindings
What are the strengths of Wat?
Extremely lightweight and minimal. Perfect for learning WebAssembly internals. Direct control over Wasm structure and instructions. Readable and easy to experiment with. Useful for debugging compiler output
What are the limitations of Wat?
Not suitable for large-scale application development. No high-level abstractions (loops, structs, variables). Verbose for anything beyond small modules. Hard to maintain manually. Manual memory management required
How can I practice Wat typing speed?
CodeSpeedTest offers 10+ real Wat code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.