Google Ink is a proprietary freehand drawing library, powered by WebAssembly, which powers Google Apps like Chrome Canvas and Google Keep. It also provides the PDF annotation feature in Chrome OS.

Ink uses WebAssembly, and WebAssembly threads, to bring a low-latency drawing experience to users. WebAssembly allows the Ink team to bring its C++/OpenGL ES drawing engine to the web with a relatively small amount of TypeScript glue code and protocol buffers.

Additonal Resources

• Analysis of Google Keep's WebAssembly module