Screen Geometry Test

A correctly configured display shows straight lines, square squares and round circles, right to the edge of the panel. These patterns make scaling errors and overscan obvious.

Lines should be straight, evenly spaced and sharp all the way to the edges.

Runs entirely in your browser. Nothing is uploaded or stored.

How to use

  1. Press Start test to go fullscreen, then use the arrow keys, the Previous and Next buttons or a tap to move between patterns.
  2. On the Grid, check that lines are straight and evenly spaced all the way to the edges.
  3. On the Circles, check that they look round, not oval. An oval means the image is stretched.
  4. On the Overscan pattern, make sure the outer border and corner markers are fully visible. If they are cut off, the display or TV is overscanning.
  5. Use the Crosshair to check that the image is centered and the diagonals reach the corners.
  6. Press Invert to swap to a white background if thin lines are hard to see on black.

What this test can detect

  • Stretched or squashed images from a wrong aspect ratio setting.
  • Overscan on TVs, where the edges of the picture are cut off.
  • Non-native resolution or scaling that softens lines.
  • Off-center or shifted images on projectors and TVs.

Important

  • Browser zoom and operating system scaling change the size of the patterns. Reset zoom to 100 percent for the ruler to be meaningful.
  • Flat panels do not suffer from the geometric distortion that CRT monitors had. Curved lines usually point to a projector, a scaler or a stretched resolution.
  • The ruler assumes the browser's nominal 96 pixels per inch and does not know the physical size of your screen.