Mouse requires two clicks to open links

Moving from one window to another window requires a click to change focus to that window.

If you are choosing a link that is in a different tab, app window, on your desktop or in finder.

Then the first click is changing the focus to where the link is and the second click is opening the link.

Bettijayne wrote:

A good example is when filling in an online form. I click on the appropriate box but the page moves slightly with my cursor thus moving away from the box. I then move my cursor back to the box, click and it will open allowing me to complete the field. Up until recently just clicking once would get me into the field

Magic Mouse has gestures. Those gestures can cause the pointer to move around, as well as other functions.

See the second section of the following for the available Magic Mouse gestures:

• https://support.apple.com/en-us/102482

As an alternative to using the mouse to navigate fields, click on the first field to gain access, then use tab through the fields. It is possible to navigate forms and fields and the whole UI entirely from the keyboard, too.

• https://support.apple.com/guide/mac-help/use-full-keyboard-access-mchlc06d1059/mac

I usually use either a Magic Trackpad, or a three-button scroll-wheel mouse, as the Magic Mouse never fit properly in my hand, and was fussy for me to use.

Your description of what's happening is not real clear.

If you are choosing a link that is in a different tab, app window, on your desktop or in finder.

Then one click is changing the focus where the link is and the second click is opening the link.

If the page and is moving a little, then that sounds more like your finger is sliding a little on the mouse and causing the window to slightly scroll.

What App are you working in and where is the link that you are trying to open..?

Again it sounds like the link that you are trying to open is in a different window or location than the App you are working in.

Bettijayne wrote:

No it’s always in the same window. All on my iMac so not always apps. Sometimes just filling in forms for example. I click and then have to click again.

Two clicks as in one click to get to the desktop, and then a click on an app or file or link?