2 min read

Wasmjit team announced last week that you can now run Nginx 1.15.3, a free and open source high-performance HTTP server and reverse proxy, in user-space on all POSIX system.

Wasmjit is a small embeddable WebAssembly runtime that can be easily ported to most environments. It primarily targets a Linux kernel module capable of hosting Emscripten-generated WebAssembly modules. It comes equipped with a host environment for running in user-space on POSIX systems. This allows you to run WebAssembly modules without having to run an entire browser. Getting Nginx to run had been a major goal for the wasmjit team ever since its first release in late July.

“While it might be convenient to run the same binary on multiple systems without modification (“write once, run anywhere”), this goal was chosen because IO-bound / system call heavy servers to stand to gain the most by running in kernel space. Running FUSE file systems in kernel space is another motivating use case that Wasmjit will soon support”, mentions the wasmjit team.

Other future goals for wasmjit includes introduction of an interpreter, rust-runtime for Rust-generated wasm files, Go-runtime for Go-generated wasm files, optimized x86_64 JIT
,arm64 JIT, and macOS kernel module.


Wasmjit running nginx has been tested on Linux, OpenBSD, and macOS so far. The complete compiled version of nginx without any modifications and with multi-process capability has been used. All the complex parts of the POSIX API that are needed for proper implementation of Nginx have been used such as signal handling and forking.

That being said, Kernel space support still needs working as Emscripten delegates some large APIs such as getaddrinfo() and strftime() to the host implementation. These need to be re-implemented in the kernel. Moreover, kernel space versions of fork(), execve(), and signal handling also need to be implemented. Also, Wasmjit is currently in alpha-level software in development and might lead to unpredictable substances when used in production.

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