Pragma Header

The Pragma header provides backward compatibility with HTTP/1.0 clients. It is mainly used for cache management and tells the server and intermediate caches that it needs a fresh version of the resource. Older clients may not support HTTP/1.1, so this header is still in use.

GET Request With Pragma Header Live Example
GET / HTTP/1.0
Pragma: no-cache
Host: www.google.com

The HTTP/1.1 caches treat "Pragma: no-cache" as if the client had sent "Cache-Control: no-cache".
No new Pragma directives will be defined in HTTP.

However, to guarantee a fresh version of the resource, many clients send three HTTP caching headers at once that works across all servers and proxies.

HTTP Headers to Prevent Caching Live Example
GET / HTTP/1.0
Host: www.google.com			
Cache-Control: no-cache, no-store, must-revalidate
Pragma: no-cache
Expires: 0

Unlike the Cache-control header, Pragma is only applicable to client requests, while Cache-Control can be used along the whole request-response chain.
Last updated: Jun 21, 2020 Viewed: 10224 times
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