Hi Matt,
Greetings from Syncfusion support.
We have validated your reported problem that Sidebar is still visible when page load.
In all browser’s workflow, first it will render the HTML elements of a HTML page. Then, the styles and scripts of the corresponding page will be compiled for applying it to the already available HTML elements in the page for draw the structural design of that HTML page.
On initial rendering Sidebar’s HTML element appears on the screen with window width, and then modifies to its actual structural dimesion due to the above described browser behavior. Your reported problem occurs.
To overcome this problem, we can added a class “e-hidden”(which has Style property has display as none) which hides the Sidebar element while its render is in progress, then we can remove the class from the Sidebar element on its created event, which will meet your requirement of initializing Sidebar in collapsed state.
Please, check out the sample with the above solution below.
Please, let us know if you need any further assistance.
Regards,
Shameer Ali Baig S.