Depends how you measure it. A long time ago I benchmarked it, and Lwan came out on top, performance-wise. However, performance isn't the only thing that matte

Depends how you measure it. A long time ago I benchmarked it, and Lwan came out on top, performance-wise. However, performance isn't the only thing that matters in a piece of software like this. H2O is a great project; in fact, the authors were tightly involved in the definition of HTTP/2.0, and it is one of the first servers to support this version of the protocol. It is well written, and easy to grok the code. Some of its byproducts include a nice (and reusable) HTTP parser library, and clever tool named qrintf (that pre-parses the format string passed to printf()-family functions and generates optimal code for that). Also, there's a company behind it -- Lwan is just a toy I work on the weekends when I feel like it.