PWM (Pulse-Width Modulation) dimming is a method of controlling LCD backlight brightness by rapidly switching the backlight on and off. At 50% brightness, the backlight is on for half the time and off for half the time per cycle. At lower brightness levels, the duty cycle is shorter (more off time). The flickering frequency is measured in Hz — a 1000 Hz PWM rate switches the backlight 1000 times per second. At lower PWM frequencies (100–500 Hz), some users can perceive the flicker, particularly under eye movement, which can cause eye fatigue, headaches, and blurred vision in sensitive individuals. High-frequency PWM (1000 Hz+) is generally imperceptible, and DC dimming (no PWM at all) eliminates flicker entirely.

A flicker-free monitor uses DC (Direct Current) dimming instead of PWM to adjust brightness. In DC dimming, brightness is controlled by varying the voltage supplied to the backlight LEDs — lower voltage means lower brightness, with no on/off switching and therefore no flickering at any brightness level. Most monitor manufacturers that advertise "flicker-free" have independently verified their DC dimming technology. BenQ, Dell, LG, and many others offer flicker-free certified monitors. The VESA Flicker Free standard requires that flicker be below the visible threshold at all brightness levels. Note that some monitors use DC dimming at high brightness but switch to PWM at low brightness levels to improve color accuracy — always test at your typical operating brightness.

Yes. For some individuals, particularly those sensitive to visual stimuli, PWM-based monitor flickering can cause a range of symptoms including eye fatigue, dry eyes, blurred vision, headaches, and difficulty focusing after extended use. The effect is most pronounced at lower brightness settings (where PWM duty cycles are shorter and flicker is more intense) and at lower PWM frequencies. Scientific research on flicker sensitivity shows considerable individual variation — some people are unaffected by 500 Hz PWM while others experience discomfort at 1000 Hz. If you experience eye strain or headaches after monitor use, flicker is one possible cause (along with blue light, improper eye distance, and uncorrected vision). Switching to a flicker-free or high-frequency PWM monitor may help.

DC (Direct Current) dimming controls LED backlight brightness by varying the electrical current or voltage supplied to the LEDs. Less current = lower brightness, continuously and without switching. PWM (Pulse-Width Modulation) dimming controls brightness by switching the LEDs on and off very rapidly — the perceived brightness is an average of the on/off states. DC dimming produces no flicker but can shift color accuracy at very low brightness levels because LED color output is slightly voltage-dependent. PWM dimming maintains consistent color accuracy across all brightness levels because the LED always operates at full power, but it introduces the flickering characteristic. Modern displays often combine both approaches — DC dimming at high brightness, PWM only at lower brightness levels.

OLED monitors and TVs handle flicker differently from LCD displays. OLED pixels are self-emitting and do not use a backlight, so PWM backlight dimming is not applicable. However, OLED displays typically use PWM to control pixel brightness at lower levels, and OLED PWM frequencies are often lower than LCD PWM — some OLED TVs and monitors use PWM rates of 240–480 Hz, which is perceptible to some users, especially at low brightness. Some OLED monitors have added high-frequency PWM modes (1000–3000 Hz) or DC-like dimming to address this. OLED flicker is distinct from the burn-in concern and is an ongoing area of sensitivity for some users. If you use an OLED monitor at lower brightness for extended periods and experience eye fatigue, OLED PWM may be a contributing factor.

Several strategies can reduce or eliminate monitor flicker. The most effective is to replace your monitor with a certified flicker-free model that uses DC dimming. Keep brightness at 70–100% — most monitors only use PWM dimming at lower brightness levels; at higher brightness settings, many monitors switch to DC dimming automatically. Enable any "flicker-free" or "eye comfort" settings in your monitor's OSD if available. For OLED monitors, check if a high-frequency PWM mode or low blue light mode is available. Use a low refresh rate mode if your monitor supports it — some monitors use lower PWM frequencies at higher refresh rates. In the interim, take regular breaks (every 20 minutes, look at something 20 feet away for 20 seconds — the 20-20-20 rule). Anti-fatigue glasses and screen overlays are generally not effective against PWM flicker.