HTTP Conditional Get for RSS Hackers
What is a conditional get?
My full-length RSS feed is about 24,000 bytes long. It probably gets updated on average twice a day, but given the current tools, people still download the whole thing every hour to see if it's changed yet. This is obviously a waste of bandwidth. What they really should do, is first ask whether it's changed or not, and only download it if it has.
The people who invented HTTP came up with something even better. HTTP allows you to say to a server in a single query: ?If this document has changed since I last looked at it, give me the new version. If it hasn't just tell me it hasn't changed and give me nothing.? This mechanism is called ?Conditional GET?, and it would reduce 90% of those significant 24,000 byte queries into really trivial 200 byte queries. [From FishBowl Blog]