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.
Example
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
<body>
...
</body>
Note
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.
