Does the notebook have PWM? Explanation: Pulse Width Modulation (PWM) is a technique used in many notebooks to control the brightness of the screen. Here is how it works: With PWM, the screen backlight turns on and off quickly. The length of the on and off cycles determines the perceived brightness. The shorter the on cycles and longer the off cycles, the darker the screen appears. The switching frequency is usually so high that the human eye does not notice the flickering. However, some people may be sensitive to PWM, which can lead to eye strain, headaches or other discomfort, especially if the frequency is below 250 Hz. However, some notebooks do not use PWM or have a very high PWM frequency, which is less problematic. It is advisable to consider this when choosing a notebook if you are sensitive to screen flicker.