OpenCPU is a system for embedded scientific computing and reproducible research. The OpenCPU server provides a reliable and interoperable HTTP API for data analysis based on R. You can either use the public servers or host your own. The OpenCPU JavaScript client library provides the most seamless integration of R and JavaScript available today. Enjoy simple RPC and data I/O through standard Ajax techniques. Check for yourself by trying the jsfiddle examples. OpenCPU uses standard R packaging to develop, ship and deploy web applications. Several open source example apps are available from Github. Any app can be used on the public server or locally within an R session.