Hi Tobi, In Firefox Options -> General page -> Performance, turn off hardware acceleration. I looked up some information about your ThinkPad and found some similar issues. Some of the suggestions were: - make sure that your graphics driver is up to date - set Performance to Maximum and lastly, depending on the age, think about replacing the battery and/or the power board.

It is possible that the GPU is disabled when you use the battery to minimize the power usage (power saving). You can possibly check this in the OS settings.

@My_Cheese_Is_Slippin' I already tried to turn off hardware acceleration but it doesn't solve the problem. Even with maximum performance the lags are there. If i set the performance on minimal settings it's running smooth with ac plugged in.

@cor-el

I used 'GPU drawing' from 'System Profiler and Benchmark' with and without ac and got the same results. That means that the GPU isn't disabled on battery right?