Do you notice any particular action which might be causing this?

Ctrl + scroll up/down = Zoom in/out

A Zoom Level indicator at the right end of the address bar will appear. Or, if you are using the Zoom Controls on your toolbar, the % value in the center will change.

Use mouse shortcuts to perform common tasks in Firefox https://support.mozilla.org/en-US/kb/mouse-shortcuts-perform-common-tasks

I know about the ctrl plus scroll, but that not the issue, my situation is like the browser is alive and doing all this zoom without my input

Are there particular sites where you notice this problem, or can it be any site, like this one?

It's odd that Microsoft Edge would start being affected at the same time, since their code is completely different. However, both browsers may adapt to system level settings such as "Make text bigger" and "Make everything bigger" as well as display resolution.

well, it started in youtube... but a user in ten forums mentioned, it could be a input device problem and I did un plugged my keyboard, it seemed ok then, so will have to see for a longer time...

Hm... unpluging the keyboard solved nothing... the zoom just increased itself while the keyboard was unplugged... why is this happening, anyone got the same problem??

Can the zoom level be reset using either

• Ctrl+0 (that's a zero)
• click the zoom level indicator in the address bar

Or is it more of a magnification effect?

Can the zoom level be reset using either

• Ctrl+0 (that's a zero)
• click the zoom level indicator in the address bar

Or is it more of a magnification effect?

yes, it can be reset, but would jump again (increase or decrease zooming)

nevermind friend, I have reinstalled my windows...