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up.protocol If-None-Match
HTTP header

This request header contains the ETag of a fragment that is being reloaded.

The server can use the header value to prevent unnecessary re-rendering of unchanged content. See Conditional requests for details and examples.

The header is only set when Unpoly knows the ETag of the loading fragment. For this the fragment must have been rendered with an ETag response header or [up-etag] attribute.


The If-None-Match header uses the same format as the ETag header:

If-None-Match: W/"55e4d42a148795d9f25f89d4"