SPDY is a replacement for HTTP, designed to speed up transfers of web pages by eliminating much of the overhead associated with HTTP. SPDY supports several optimizations that give it an edge over HTTP when it comes to speed. SPDY is gaining a great deal of traction — it has been implemented in Chrome, Firefox, and Amazon Silk, has been deployed widely by Google, and there is now SPDY support for Apache through the mod_spdy module.
We wondered what the performance of SPDY would be compared to HTTP for popular websites, using a Samsung Galaxy Nexus (running Android), a modern, SPDY-enabled browser (Chrome for Android), and a variety of pages from real websites (77 pages across 31 popular domains).
The net result is that using SPDY produced a mean page load time improvement of 23% across these sites, compared to HTTP. This is equivalent to a speedup of 1.3x for SPDY over HTTP. Much more work can be done to improve SPDY performance on 3G and 4G cellular networks, but this is a promising start.
The following graph shows the page load time for HTTP and SPDY, in milliseconds, across the 77 pages that were measured. As the graph shows, in all but one case, SPDY reduces load times, sometimes by as much as 50%.