How do I disable the sidebar in Safari?

I understand you are seeking to disable the automatic Sidebar appearance in Safari, while in Full Screen mode.

The Sidebar's appearance in that mode has been a Safari feature for well over a decade so it is unlikely Apple will be interested in changing it.

For a less than attractive workaround you can use Safari in windowed mode, in which that automatic Sidebar appearance does not occur. You can make the Safari window as large as the screen, but of course that's not the same as Full Screen mode.

Another creative workaround is to use Safari in Split View: Use apps in Split View on Mac - Apple Support. If Safari is the app to the right, it will not behave that way. You can even have Safari on both sides of Split View. Not ideal either, but it is an option, whereas completely disabling that Sidebar appearance is not.

rodfromwichita (Author)

There's a wider usefulness of Sidebar from Finder view.

And other users who reference this inquiry, may further

their understanding; given more details, as available..

How to Customize What Appears in the Finder Sidebar on Mac • macReports

//macreports.com/how-to-customize-what-appears-in-the-finder-sidebar-on-mac/

"Finder is the default app for file management and is included with releases of macOS.

Finder on a Mac is designed to manage and organize your files and applications. It allows

you to browse your files and folders, open and organize documents, and manage your

applications. An essential part of the Finder windows is the sidebar. This Sidebar, located

on the left side, & it enables you to have quick access to items you use often." ~from link.

Customize the Finder toolbars on Mac - Apple Support (macOS10.13~macOS15.x)

//support.apple.com/guide/mac-help/customize-the-finder-toolbars-on-mac-mchlp3011/12.0/mac/12.0

How to Remove an Item from the Finder Sidebar on a Mac - wikihow.tech

//www.wikihow.tech/Remove-an-Item-from-the-Finder-Sidebar-on-a-Mac

How to Modify the Mac Finder Sidebar - UMA Technology

//umatechnology.org › how-to-modify-the-mac-finder-sidebar

..Hopefully these options cross boundaries where vagary may exist..

Which app are you asking about please?

If 12.7 is same as present OS then open Safari then click on view in menu bar then select hide side bar