White Screen for Monitor
Fullscreen on a desktop display, with multi-monitor notes.
Simulated dimming — browsers can't raise a panel's backlight.
Desktop-specific notes
Multi-monitor setups. Going fullscreen only fills the display the browser window is currently on. If you’re testing a second or third monitor, drag the browser window to that display first, then click Go fullscreen — the Fullscreen API targets whichever screen the window is on at the time.
The monitor’s own OSD brightness matters more than ours. The on-screen brightness slider here is a software dimming overlay — it can only make the display appear darker, never brighter. For an accurate uniformity or backlight bleed check, set the monitor’s own hardware brightness (via its OSD menu buttons) to a mid-range level first, rather than relying on this tool’s overlay.
Refresh rate and adaptive sync. If your monitor supports G-Sync or FreeSync, some browsers cap fullscreen content to a fixed rate rather than the display’s variable range — the refresh rate test here is a rough estimate for exactly this reason, not a substitute for the monitor’s own diagnostic mode if it has one.
Keyboard shortcuts still work in fullscreen — F to toggle, Esc to exit — which matters if your monitor’s physical buttons are hard to reach once you’re fullscreen on a second display.
Full monitor check
For the complete sequence — dead pixels, backlight bleed, uniformity, contrast, colour and gradient — see the monitor test hub, or read how to test a new monitor before the return window closes.