Difference between Pragma and Cache-Control headers

Question

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

User · Accepted Answer

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

User · Answer

There is no difference  except that Pragma is only defined as applicable to the requests by the client  whereas Cache-Control may be used by both the requests of the clients and the replies of the servers   So  as far as standards go  they can only be compared from the perspective of the client making a requests and the server receiving a request from the client   The http   www w3 org Protocols rfc2616 rfc2616-sec14 html sec14 32 defines the scenario as follows      HTTP 1 1 caches SHOULD treat  Pragma  no-cache  as if the client had   sent  Cache-Control  no-cache   No new Pragma directives will be   defined in HTTP     Note  because the meaning of  Pragma  no-cache as a response   header field is not actually specified  it does not provide a   reliable replacement for  Cache-Control  no-cache  in a response    The way I would read the above    if you re writing a client and need no-cache    just use Pragma  no-cache in your requests  since you may not know if Cache-Control is supported by the server  but in replies  to decide on whether to cache  check for Cache-Control  if you re writing a server    in parsing requests from the clients  check for Cache-Control  if not found  check for Pragma  no-cache  and execute the Cache-Control  no-cache logic  in replies  provide Cache-Control     Of course  reality might be different from what s written or implied in the RFC

User · Answer

Stop using  HTTP 1 0  Replaced with  HTTP 1 1 since 1999      Expires   date  Cache-Control  max-age  seconds    Pragma   no-cache Cache-Control  no-cache     If it s after 1999  and  you re still using Expires or Pragma  you re doing it wrong  I m looking at you Stackoverflow   200 OK Pragma  no-cache Content-Type  application json X-Frame-Options  SAMEORIGIN X-Request-Guid  a3433194-4a03-4206-91ea-6a40f9bfd824 Strict-Transport-Security  max-age 15552000 Content-Length  54 Accept-Ranges  bytes Date  Tue  03 Apr 2018 19 03 12 GMT Via  1 1 varnish Connection  keep-alive X-Served-By  cache-yyz8333-YYZ X-Cache  MISS X-Cache-Hits  0 X-Timer  S1522782193 766958 VS0 VE30 Vary  Fastly-SSL X-DNS-Prefetch-Control  off Cache-Control  private   tl dr  Pragma is a legacy of HTTP 1 0 and hasn t been needed since Internet Explorer 5  or Netscape 4 7  Unless you expect some of your users to be using IE5  it s safe to stop using it    Expires   date   deprecated - HTTP 1 0  Pragma  no-cache  deprecated - HTTP 1 0  Cache-Control  max-age  seconds  Cache-Control  no-cache  must re-validate the cached copy every time   And the conditional requests   Etag  entity tag  based conditional requests  Server  Etag  W    1d2e7   1648e509289    Client  If-None-Match  W    1d2e7   1648e509289    Server  304 Not Modified   Modified date based conditional requests  Server  last-modified  Thu  09 May 2019 19 15 47 GMT Client  If-Modified-Since  Fri  13 Jul 2018 10 49 23 GMT Server  304 Not Modified    last-modified  Thu  09 May 2019 19 15 47 GMT

[http] Difference between Pragma and Cache-Control headers?

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