SPDY (pronounced as speedy) is an application-layer protocol developed at Google for transporting web content.
It is not replacement of HTTP. Just modifies the way HTTP requests and responses are sent over the wire.
Why it is used?
SPDY is used to reduce the load time of web page by multiplexing and compresion.
What are problem with HTTP?
- HTTP does not have multiplexing HTTP pipelining is susceptible to head of line blocking verbose headers Requirement to use SPDY.
- SPDY requires the SSL/TLS (with TLS extension ALPN required).
How its works?
When request sent over SPDY, HTTP requests are processed, tokenized, simplified and compressed.
SPDY prioritizing and multiplexing the transfer of web page so that only one connection per client is required.
How it reduced the load time of website?
- Avoid multiple request by concatenate the JS, CSS files
- Image spriting
- Resource inlining
- It simplified and compress the request.
Who Use/Support the SPDY?
- Firefox supports SPDY 2 from version 11.
- Opera browser added support for SPDY as of version 12.10.
- Internet Explorer 11 added support for SPDY version 3.
- Google Chrome/Chromium
- Amazon's Silk browser for the Kindle Fire uses the SPDY protocol to communicate
- Facebook Makes Itself a Bit More SPDY
See Features of SPDY http://www.chromium.org/spdy/spdy-whitepaper