When you hold down the ctrl key and then scroll the wheel in the QQ chat window, the content in the chat window will become larger or smaller, which is very similar to a browser. The solution is as follows:

Method 1: Click the right mouse button in the chat window and select 100% or other display ratio.

Method 2: Hold down the ctrl key, and then toggle the wheel to change the display size.

In addition, you can use the scroll bar on the right side of the chat window to scroll up and down.

I hope I can help you.