Wasmjit is a small embeddable WebAssembly runtime. Its core is written in C90 and is easily portable to most environments.

Its primary target is a Linux kernel module that can host Emscripten-generated WebAssembly modules. In this configuration it runs WebAssembly modules in kernel-space (ring 0) and provides access to system calls as normal function calls. This configuration avoids user-kernel transition overhead, as well as scheduling overheads from swapping page tables. This results in a significant performance increase for syscall-bound programs like web servers or FUSE file systems.