Screen flickering (the whole display flashing) is caused by incompatible display drivers, refresh rate issues, or hardware problems. First, determine the cause: open Task Manager (Ctrl+Shift+Esc) — if Task Manager also flickers, it's a driver issue; if Task Manager stays stable while everything else flickers, it's an app issue. For driver issues: update your display driver from the manufacturer (NVIDIA, AMD, Intel) website, or roll back to a previous version if flickering started after an update. For app issues: uninstall recently installed apps, especially those that modify the display (f.lux, transparency tools). Change your refresh rate: Settings > Display > Advanced display > try a different rate. Check your display cable — a damaged or loose cable causes intermittent flickering. For external monitors, try a different cable (DisplayPort vs HDMI). If the monitor itself flickers independently of the computer, it's a hardware issue with the monitor's backlight.