Set up the whole available screen
On iPhone, iPad or Android, begin with the device at comfortable brightness and clean the display according to its instructions. Check whether a removable protector, surface speck or overlay explains the mark before treating it as a panel fault.
- iPhone: if Safari cannot hide the browser bars, use Share → Add to Home Screen, then open the saved site and hide the test controls. System indicators and the camera area can still cover part of the display.
- iPad: expand the browser out of a split or floating window before testing. Use the test’s Full screen button when available, then hide controls. Rotate and repeat to inspect areas near system controls.
- Android: request fullscreen from the test controls. Browser support varies; rotate and repeat if navigation controls still cover an edge.
- Any phone or tablet: a browser color test does not test touch accuracy, cameras, proximity sensors or every physical pixel behind a cutout.
For an OLED iPhone with a faint retained image, Apple distinguishes temporary persistence from long-term burn-in and recommends avoiding prolonged static images at maximum brightness. Read Apple’s OLED display guidance and use our retention comparison.
What to look for
- Clean the screen and inspect the protector first.
- Browser controls may remain visible on iOS; the screen-filling color view still uses the available browser area.
- Disable color filters, extra-dim modes, and screen overlays while checking.
- Use another camera to photograph a physical defect.
Use this order
- Rotate to the orientation where the mark is easiest to inspect.
- Run black and white.
- Run RGB manually.
- Take and view a screenshot on another display.
- Use the phone maker’s built-in diagnostic/support flow if the mark remains.