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up.protocol X-Up-Version
HTTP header

This request header contains the current Unpoly version to mark this request as a fragment update.

Server-side code may check for the presence of an X-Up-Version header to distinguish fragment updates from full page loads.

The X-Up-Version header is guaranteed to be set for all requests made through Unpoly.


The user updates a fragment. Unpoly automatically includes the following request header:

X-Up-Version: 1.0.0

The server chooses to render different HTML to Unpoly requests, e.g. by excluding the document <head> and only rendering the <body>. The server responds with the folowing HTTP:

Vary: X-Up-Version



Request headers that influenced a response should be listed in a Vary response header. This tells Unpoly to partition its cache for that URL so that each request header value gets a separate cache entries.