Caching Tutorial

for Web Authors and Webmasters

What’s a Web Cache? Why do people use them?
Kinds of Web Caches
Browser Caches
Proxy Caches
Aren’t Web Caches bad for me? Why should I help them?
How Web Caches Work
How (and how not) to Control Caches
HTML Meta Tags vs. HTTP Headers
Pragma HTTP Headers (and why they don’t work)
Controlling Freshness with the Expires HTTP Header
Cache-Control HTTP Headers
Validators and Validation
Tips for Building a Cache-Aware Site
Writing Cache-Aware Scripts
Frequently Asked Questions
Implementation Notes — Web Servers
Implementation Notes — Server-Side Scripting
References and Further Information
About This Document