A first look at HTTP/3 adoption and performance

The third version of the Hypertext Transfer Protocol (HTTP) is in the final standardization phase by the IETF. In addition to better security and greater flexibility, it promises performance benefits. HTTP/3 uses a more efficient header compression scheme and replaces TCP with QUIC, a transport protocol over UDP that was originally proposed by Google and is also currently being standardized. Although initial implementations of HTTP/3 already exist and some websites have announced their support, few studies have been conducted to assess its benefits. We measure the adoption and performance of HTTP/3 and show how it has been adopted by some of the leading Internet companies such as Google, Facebook, and Cloudflare in 2020. We conduct a large-scale measurement campaign on thousands of websites using HTTP/3 to understand the extent to which it outperforms HTTP/2 in web browsing applications. We find that websites using HTTP/3 often host most web page objects on third-party servers that only support HTTP/2 or even HTTP/1.1. Websites that load objects from a limited number of third-party domains are the ones that see larger performance gains. However, our experiments show that HTTP/3 offers significant benefits only in high-latency or mobile networks. Finally, we run an experimental campaign to study the impact of HTTP/3 on video streaming applications. In this direction, our results show that HTTP/3 currently does not provide benefits