The C/C++ compiler for web applications

Cheerp 3.0 released

Cheerp is an open-source C/C++ to WebAssembly compiler. It compiles virtually any C/C++ code to WebAssembly and JavaScript.

#include <cheerp/client.h>
void webMain() {
client::window.alert("Hello Cheerp");

What is Cheerp?

Cheerp is a C/C++ compiler to WebAssembly and JavaScript, based on and integrated into the LLVM/Clang infrastructure, and featuring numerous custom optimisation steps to maximise performance and minimise size of the compiled JavaScript/WebAssembly output. Thanks to this, Cheerp is the best performing, most optimised C++ to WebAssembly compiler available on the market.

Cheerp is used primarily to port existing C/C++ libraries and applications to HTML5, but can also be used to write high-performance Web applications and WebAssembly components from scratch. Using Cheerp, C/C++ code gets compiled into JavaScript/WebAssembly and optimised, with the right JavaScript interfaces being exposed, and can easily be integrated in a web application.

Cheerp is licensed under the “Apache 2.0 License with LLVM exceptions”, i.e. the same license of upstream LLVM/Clang. This is a permissive license that allows virtually any use of the software.

What’s unique about Cheerp?

Cheerp enables C/C++ code to be compiled to a combination of WebAssembly and JavaScript (or asm.js when targeting legacy browsers). Compared to alternative C/C++ compilers for web applications such as Emscripten, Cheerp:

  1. Generates more optimized (smaller) WebAssembly code, but can also compile to a JavaScript output with dynamic memory (garbage-collectible output), zero-overhead DOM manipulation and access to Web APIs and superior C++-JavaScript interoperability.
  2. Allows one to compile a single code base into a combination of WebAssembly and JavaScript by (optionally) tagging portions of the code with [[cheerp::genericjs]] and [[cheerp::wasm]].


If you have any questions about Cheerp, join the Cheerp community on Discord.

Bugs and feature requests

Please create a GitHub issue!


Cheerp is free open-source software, actively developed and maintained by Leaning Technologies. Commercial support, feature fast tracking, sponsored development and consulting packages are available for Enterprise customers.

Was this page helpful?
Suggest changes