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A Swarm client or proxy can include this header with a GET, PUT, or DELETE method. All other methods ignore this header when present in the request. The If-Unmodified-Since request header field is used with a method to make it conditional.
If the requested object was not modified since the time specified in this field, Swarm performs the requested method as if the If-Unmodified-Since header were is not present .If if the requested object was is not modified since the specified time, time specified in this field.
Swarm does not perform the requested method, and instead, return returns a 412 Precondition failed if the requested object is modified since the specified time.
If The header is ignored if the specified date is invalid, the header is ignored.
Expires
Swarm returns an Expires header if it is persisted with the content. Swarm does not generate an Expires header.
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