This request header contains the targeted layer's mode.
Server-side code is free to render different HTML for different modes. For example, you might prefer to not render a site navigation for overlays.
The user updates a fragment
main within a drawer overlay.
Unpoly automatically includes the following request headers:
X-Up-Mode: drawer X-Up-Target: main
The server chooses to render only the HTML required for the overlay. It responds with the following HTTP:
Vary: X-Up-Mode <main>...</main>
Request headers that influenced a response should be listed in a
Varyresponse header. This tells Unpoly to partition its cache for that URL so that each request header value gets a separate cache entries.