WebAssembly is a binary instruction format for a stack-based virtual machine, designed as a portable compilation target for high-level languages like C/C++, Rust, Go, Java, and Kotlin. Standardized as WebAssembly 3.0 by the W3C in September 2025, it runs at near-native performance in a sandboxed environment and supports a rich feature set including garbage collection, exception handling, 64-bit memory, SIMD, and threading. Unlike JavaScript, core Wasm is statically typed with numeric, vector, and reference types, enabling predictable performance ideal for compute-intensive workloads like gaming, video processing, scientific computing, and server-side edge functions. The key insight: Wasm isn't meant to replace JavaScript—it complements it, handling performance-critical code while JS manages the DOM and user interactions.
What This Cheat Sheet Covers
This topic spans 29 focused tables and 293 indexed concepts. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.
Table 1: Core Value Types
| Type | Example | Description |
|---|---|---|
(i32.const 42) | • 32-bit integer • not inherently signed or unsigned—interpretation determined by operation. | |
(i64.const 9223372036854775807) | • 64-bit integer • used for large numbers, memory addresses in Memory64 proposal. | |
(f32.const 3.14) | 32-bit floating-point number following IEEE 754 standard. | |
(f64.const 2.718281828) | • 64-bit floating-point number following IEEE 754 • default for most floating operations. | |
(v128.const i32x4 1 2 3 4) | • 128-bit vector for SIMD operations • holds multiple values processed in parallel. | |
(table 10 funcref) | • Nullable reference to any function • shorthand for (ref null func). |