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What does the HTTP header Pragma: Public mean?
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The Pragma HTTP/1.0 general header is an implementation-specific header that may have various effects along the request-response chain. This header serves for backwards compatibility with the HTTP/1.0 caches that do not have a Cache-Control HTTP/1.1 header.
To check the Pragma in action go to Inspect Element -> Network check the header for Pragma like below. Pragma header is highlighted.
"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.
Cache-control is an HTTP header used to specify browser caching policies in both client requests and server responses. Policies include how a resource is cached, where it's cached and its maximum age before expiring (i.e., time to live).
According to the standard, Pragma is implementation dependent (section 14.32), except for no-cache because of its wide use. Cache-Control (section 14.9) is the proper way to control caching. This is what the standard says for a Cache-Control: public:
Indicates that the response MAY be cached by any cache, even if it would normally be non-cacheable or cacheable only within a non- shared cache.
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Also, "Pragma: Public" is used in Google App Engine applications to enable caching of responses within its Edge Cache.
See Details on Google App Engine's caching proxy?
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