Difference between Pragma and Cache-Control headers?

http http-headers request protocols httpresponse
saplingPro picture saplingPro · Apr 25, 2012 · Viewed 177.1k times · Source

I read about Pragma header on Wikipedia which says:

"The Pragma: no-cache header field is an HTTP/1.0 header intended for use in requests. It is a means for the browser to tell the server and any intermediate caches that it wants a fresh version of the resource, not for the server to tell the browser not to cache the resource. Some user agents do pay attention to this header in responses, but the HTTP/1.1 RFC specifically warns against relying on this behavior."

But I haven't understood what it does? What is the difference between the Cache-Control header whose value is no-cache and Pragma whose value is also no-cache?

Answer

Eric Brenden picture Eric Brenden · Apr 25, 2012

Pragma is the HTTP/1.0 implementation and cache-control is the HTTP/1.1 implementation of the same concept. They both are meant to prevent the client from caching the response. Older clients may not support HTTP/1.1 which is why that header is still in use.

Related questions

Python send POST with header

I try to build a python script who sends a POST with parameters for extracting the result. With fiddler, I have extracted the post request who return that I want. The website uses https only. POST /Services/GetFromDataBaseVersionned HTTP/1.1 Host: …

Read More
application/x-www-form-urlencoded or multipart/form-data?

In HTTP there are two ways to POST data: application/x-www-form-urlencoded and multipart/form-data. I understand that most browsers are only able to upload files if multipart/form-data is used. Is there any additional guidance when to use one of …

Read More
How do we control web page caching, across all browsers?

Our investigations have shown us that not all browsers respect the HTTP cache directives in a uniform manner. For security reasons we do not want certain pages in our application to be cached, ever, by the web browser. This must …

Read More