Measuring HTTP/3: Adoption and Performance

The third version of the Hypertext Transfer Proto- col (HTTP) is in its final standardization phase by the IETF. Be- sides better security and increased flexibility, it promises benefits in terms of performance. HTTP/3 adopts a more efficient header compression schema and replaces TCP with QUIC, a transport protocol carried over UDP, originally proposed by Google and currently under standardization too. Although HTTP/3 early implementations already exist and some websites announce its support, it has been subject to few studies. We provide a first measurement study on HTTP/3 adoption and performance. We testify how it has been adopted by some of the leading Internet companies such as Google, Facebook and Cloudflare in 2020. We run a large-scale measurement campaign towards thousands of websites adopting HTTP/3, aiming at understanding to what extent it achieves better performance than HTTP/2. We find that adopting websites often host most web page objects on third- party servers, which support only HTTP/2 or even HTTP/1.1. As excepted, websites loading objects from a limited set of third- party domains (avoiding legacy protocols) are those experiencing larger performance gains. Our experiments however show that HTTP/3 provides sizable benefits only in scenarios with high latency or poor bandwidth.