WebAssembly lets code written in languages like Rust, C++ or Go run in the browser at close to native speed, and the pitch — near-native performance on the web — makes it tempting to reach for on any project with a performance complaint. Most web applications' performance problems are not computational; they're network latency, unoptimised rendering, or too much JavaScript shipped to the client, none of which WebAssembly fixes.
Where it genuinely earns its place is computationally heavy work that would be slow in JavaScript regardless of how well-optimised the code is: image or video processing in the browser, a physics simulation, cryptographic operations, or running an existing native library — a PDF renderer, a compression algorithm — without rewriting it. If the bottleneck is CPU-bound computation rather than anything network or rendering related, WebAssembly is solving the actual problem.
The build complexity it adds is real and worth weighing honestly. A WebAssembly module needs its own build toolchain, usually in a different language from the rest of the application, and debugging it inside a browser is meaningfully harder than debugging JavaScript with familiar developer tools. For a team without existing Rust or C++ expertise, the learning curve alone can exceed the performance gain for anything short of a genuinely compute-heavy workload.
The pragmatic test before adopting it: profile the actual bottleneck first, in the browser's own performance tools, rather than assuming. Teams that reach for WebAssembly on instinct frequently find the real slowdown was a rendering issue or an oversized JavaScript bundle, both of which are considerably cheaper to fix than standing up a second toolchain.
