It's mostly a session framework on top of SSL but under HTTP. From http://dev.chromium.org/spdy/spdy-whitepaper http://dev.chromium.org/spdy/spdy-whitepaper Q

It's mostly a session framework on top of SSL but under HTTP. From http://dev.chromium.org/spdy/spdy-whitepaper http://dev.chromium.org/spdy/spdy-whitepaper Q: Is SPDY a replacement for HTTP? A: No. SPDY replaces some parts of HTTP, but mostly augments it. At the highest level of the application layer, the request-response protocol remains the same. SPDY still uses HTTP methods, headers, and other semantics. But SPDY overrides other parts of the protocol, such as connection management and data transfer formats.