This request header contains the CSS selector targeted for a successful fragment update.
Server-side code is free to optimize its response by only rendering HTML that matches the selector. For example, you might prefer to not render an expensive sidebar if the sidebar is not targeted.
Unpoly will usually update a different selector in case the request fails.
This selector is sent as a second header,
The user may choose to not send this header by configuring
X-Up-Target: .menu X-Up-Fail-Target: body
The server may change the render target context by including a CSS selector as an
in its response.
Content-Type: text/html X-Up-Target: .selector-from-server <div class="selector-from-server"> ... </div>
The frontend will use the server-provided target for both successful (HTTP status
and failed (status
The server may also set a target of
:none to have the frontend render nothing.
In this case no response body is required:
Content-Type: text/html X-Up-Target: :none