Single-click acting like double-click on Mac

No, Apple didn't change anything. Try a different mouse.

I understand a single click of your mouse button is acting as though you double-clicked it, the result is that apps are opening or other behavior you don't want.

The normal single-click behavior is to select something, position a cursor, etc.

Apple has not changed anything about that behavior since its original inception in 1984 or so.

Please determine if the same problems occur in "Safe Mode": Start up your Mac in safe mode - Apple Support

Your text is a bit confusing... when you click once, it is a single click; did you mean to say

that it acts as a DOUBLE click? On another passage, you say that it adds to your selection - that would be a SHIFT-click (i.e. clicking while also keeping the Shift key down), or perhaps (depending on context) a COMMAND-click.

Please clarify.

Also, please tell us which pointing device you are using - trackpad (like the one built into every mac laptop), mouse (and which one). If you can, test with a different trackpad or mouse, to determine if it may be hardware related.

Oh, and no, there have been no changes on how each type of click is supposed to work.

Rich Allcorn wrote:

... 40+yrs in IT, I did that first.

Then it sounds like you will need to use the nuclear option, a complete erase and reinstall of macOS. If you have double checked your mouse options, tried a different mouse, restarted your Mac in Safe Mode, and nothing fixes it then something has gone wrong internally. As has been pointed out Apple has changed nothing regarding how a mouse works in macOS Sequoia 15.6.1.

It's always good to start fresh sometimes.

Couldn't agree more. I normally build our Macs from scratch with each major OS release to make sure nothing is there that isn't supposed to be.

Last year when Sequoia was released, I rebuilt my M4 Pro mini, but I got lazy and just installed it over the previous OS on my wife's M2 Pro mini. She's had odd issues on her Mac ever since. All only annoying but workable until the latest Acrobat update. Now it hangs every time she tries to close the app, requiring a Force Quit. It behaves as expected in new account, so the issue is somewhere in her normal account. But being this close to Tahoma's release, I'm not going on a hunt for the problem. I'll just rebuild it then.

Rich Allcorn wrote:

I use a Logitech MXAnywhere 2 mouse. I've been using it for a long time.

Thanks for the help ...

Have you installed the Logitech customization software/extension? If so, that could be the source of the problem.

No change from the Apple side.

Mouse settings on Mac - Apple Support