Why does Web Server respond “304 Not Modified” when no Etag and no “If-Modified-Since” is in request header
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13-09-2020 - |
Question
I get back
304 Not Modified
from the web server, but in Firebug, the request header doesn't have Etag and doesn't have If-Modified-Since
, and I looked at all the header line and there was no datetime info at all, so how does the server know the content is not modified?
Solution
The "ETag" header is sent by the server in the response - the client sends an "If-None-Match" back to the server with the ETag value if it already has it cached.
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