Spdy may not be significantly faster than http or https

A web performance researcher states after running a series of tests that the spdy protocol is actually slightly slower than the http protocol. Spdy would perform slightly better than encrypted https connections.

Researcher Guy Podjarny describes on his blog how he conducted tests with the top 500 websites from the Alexa list. He placed these websites behind the proxy service Cotendo, and then retrieved them via the Chrome browser. In addition, http, https and spdy connections were set up via both slow and lightning-fast internet connections. The researcher also did not use a client-side proxy in his measurements, but a reverse proxy, which is a more realistic scenario in Podjarny’s opinion.

According to Podjarny, the test results show that spdy is approximately 4.5 percent faster than https and on average even 3.4 percent slower than unencrypted connections that run via http. According to the web performance researcher, there are various reasons why less speed gain is achieved with spdy in practice than various other researchers state. For example, many websites use content from many third party domains, but because spdy optimizes connections per domain, the number of http connections does not decrease significantly. Furthermore, for many websites http would not be the main bottleneck when it comes to performance; often it is unoptimized scripts or css code that make a site viscous.

The researcher concludes that while spdy is a solid protocol, site builders who want to use the protocol should not have too high expectations. In addition, the developers of the spdy protocol, which can mainly be found within Google, can also implement various optimizations to make the ‘http 2.0 candidate’ perform better. For example, spdy could offer even more ‘aggressive’ content while the browser is still processing javascript and css. However, this also requires further improvements in the various browsers that can handle spdy.