WebAssembly comes to Vercel Edge Functions
Vercel has added WebAssembly (Wasm) support to Edge Functions, letting developers compile edge code from languages including Rust, Go, and C. The move is aimed at teams that need the speed of edge execution but have logic written in languages other than JavaScript, or that need to crunch heavy computational workloads faster than JS allows.
WebAssembly is a low-level language comparable to Assembly that acts as a compilation target for many programming languages. It's commonly supported by JavaScript virtual machines, including the V8 engine that powers Vercel's open-source Edge Runtime. Support for Wasm makes existing libraries portable directly into edge functions.
Edge code without rewriting
A key advantage of Wasm at the edge is reuse: existing libraries in C, Rust, or other languages can be compiled to Wasm and used directly in an Edge Function. Examples include libpng, the C-based PNG image generator, or even PHP applications. For developers already using Vercel Functions because of a C or Rust dependency, recompiling that code to Wasm opens the door to moving it to Edge Functions.
This is especially useful for workloads that process binary data through bitwise operations. C-like languages handle tasks like bitshifting and XORs naturally. For instance, this line from the splitmix32 PRNG:
z = (z ^ (z >> 16)) * 0x85ebca6b;
While that line also parses as JavaScript, the language's arithmetic semantics produce a different result. JavaScript requires workarounds such as Math.imul and the unsigned right shift operator (>>>) to operate over unsigned 32-bit integers:
z = Math.imul((z ^ (z >>> 16)), 0x85ebca6b);
Both languages reach the same outcome, but JavaScript demands extra functions and operators — and skipping them introduces subtle bugs. WebAssembly lets developers write idiomatic code in the language they prefer and deploy it at the edge.
Performance gains for intensive compute
Beyond language portability, Wasm is often faster than equivalent JavaScript. Vercel's edge network is tuned for running JS, but for computationally heavy workloads, WebAssembly runs roughly 2–3 times faster. Compilers can also use SIMD extensions to further optimize arithmetic.
A demo comparing two edge functions — one in JavaScript, one in C compiled to Wasm — solves a maze using the "right-hand rule" and renders an SVG of each solve:
The maze-solving benchmark shows the Wasm version performing more than twice as fast. For tight loops and number-crunching code, WebAssembly is generally the fastest execution path available in Vercel Edge Functions.
Getting started
New projects should use Vercel Functions with the Node.js runtime and Fluid compute, and Routing Middleware for request-time routing. For current projects, refer to the WebAssembly runtime reference and Vercel Functions documentation. Existing Edge Runtime projects can continue to use WebAssembly where it's supported.
