Microsoft has been deploying FPGAs in every Azure server over the last several years, creating a cloud that can be reconfigured to optimize a diverse set of applications and functions. This configurable cloud provides more efficient execution than CPUs for many scenarios without the inflexibility of fixed-function ASICs at scale. Today, Microsoft is already using FPGAs for Bing search ranking, deep neural network (DNN) evaluation, and software defined networking (SDN) acceleration. Azure’s FPGA-based accelerated networking reduces inter-virtual machine latency by up to 10x while freeing CPUs for other tasks. We describe Microsoft’s cloud FPGA architecture, show how these applications are using it, show live demos of the performance that FPGAs provide, and discuss possible uses.