Need help with wasi-libc?
Click the “chat” button below for chat support from the developer who created it, or find similar developers for support.

About the developer

444 Stars 87 Forks Other 222 Commits 35 Opened issues


WASI libc implementation for WebAssembly

Services available


Need anything else?

Contributors list


WASI Libc is a libc for WebAssembly programs built on top of WASI system calls. It provides a wide array of POSIX-compatible C APIs, including support for standard I/O, file I/O, filesystem manipulation, memory management, time, string, environment variables, program startup, and many other APIs.

WASI Libc is sufficiently stable and usable for many purposes, as most of the POSIX-compatible APIs are stable, though it is continuing to evolve to better align with wasm and WASI.


The easiest way to get started with this is to use wasi-sdk, which includes a build of WASI Libc in its sysroot.

Building from source

To build a WASI sysroot from source, obtain a WebAssembly-supporting C compiler (currently this is only clang 8+, though we'd like to support other compilers as well), and then run:

make WASM_CC=/path/to/clang/with/wasm/support \
     WASM_AR=/path/to/llvm-ar \

This makes a directory called "sysroot", by default. See the top of the Makefile for customization options.

To use the sysroot, use the

/path/to/wasm/supporting/c/compiler --sysroot=/path/to/the/newly/built/sysroot ...

to run the compiler using the newly built sysroot.

Note that Clang packages typically don't include cross-compiled builds of compiler-rt, libcxx, or libcxxabi, for

, libc++.a, or libc++abi.a, respectively, so they may not be usable without extra setup. This is one of the things wasi-sdk simplifies, as it includes cross-compiled builds of compiler-rt, libc++.a, and libc++abi.a.

Arch Linux AUR package

For Arch Linux users, there's an unofficial AUR package tracking this git repo that can be installed under the name wasi-libc-git.

We use cookies. If you continue to browse the site, you agree to the use of cookies. For more information on our use of cookies please see our Privacy Policy.