Avoiding 304 (not modified) responses
The Expires:
header your server sends out has nothing to do with future 304 responses. It provides only an estimate to clients/proxies for how long they can wait before considering a resource "stale." Clients aren't required to observe this header and are free to continue making new requests for the same resource if they wish. So, to answer your question in short:
No, you'll never be able to explicitly prevent users from making new requests for the same resource regardless of what headers you send.
The 304 response is the result of a matching If-Match
or If-Modified-Since
header in the client request. What's happening here is your server is sending out either/or/both of the following headers with its original response:
ETag
Last-Modified
Clients then send back the following headers with their requests to see if the resource has changed from their cached version:
-
If-Match
(ETag) -
If-Modified-Since
(Last-Modified)
If either of these conditions is true then the server will send the 304 Not Modified
response you've observed and the client will know it can safely serve up its cached version of the resource.
Compliance Note
RFC 2616 Section 14.21 actually prohibits compliant servers from sending Expires
headers more than one year in the future, so you shouldn't be using "access plus 10 years" in the first place:
HTTP/1.1 servers SHOULD NOT send Expires dates more than one year in the future.
That Brazilian Guy
Living in the Buenos Aires jungle, surrounded by monkeys, wearing a sombrero, dancing the samba. I make a lot of really unfunny jokes and complain about the price of gadgets in my country. Fluent in Brazilian Spanish.
Updated on July 24, 2022Comments
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That Brazilian Guy over 1 year
Is it an
ExpiresDefault
Apache directive enough to avoid HTTP Status 304 responses from the server? I have setExpiresDefault "access plus 10 years"
but I'm still seeing log entries with a 304 response for"GET /assets/template/default/css/style.min.css?v=1 HTTP/1.1"
whenever I open any page on a local PHPMyFAQ site. Emptying the browser cache doesn't seem to change anything. -
Szabolcs Páll over 8 yearsSHOULD NOT !== MUST NOT (not prohibited, just not recommended: ietf.org/rfc/rfc2119.txt)