Speeding up Web Apps performance with WebAssembly and Emscripten

WebAssembly enables running native C/C++ code in the browser at near-native performance. It allows us to bring the raw speed of native C/C++ libraries into the browser, making advanced software accessible without the need for rewriting everything from scratch or dealing with complex local installations. At the heart of this is Emscripten, a complete SDK that bridges the gap between native code and JavaScript, enabling near-native execution speeds in a web environment.

In this session, I will demonstrate the significant difference Wasm makes by comparing popular JavaScript crypto libraries with the battle-tested secp256k1 implementation from bitcoin-core. We’ll dive into the real-world engineering behind the PrivMX integration – a privacy-focused toolkit for simple implementation of end-to-end encryption in communication channels – showing how we use Emscripten to port a complex library and handle high-performance operations.

You’ll learn where JavaScript hits a performance wall and how WebAssembly fills the gap, how to navigate the Emscripten SDK to compile, and bridge C++ libraries into a JavaScript environment. You will also see the tangible performance gains of using compiled C++ over native JS for elliptic curve operations (Secp256k1). Having implemented WebAssembly in the PrivMX stack, we have learned some practical lessons that I would like to share with you.