What is EDID (how a TV tells a console what it can show)?
In one sentence: The menu card a TV or monitor hands over when you plug it in: its name, every picture mode it can show and whether it can do HDR, so the device can pick one.
A little more
EDID (Extended Display Identification Data) is a small block of facts stored on a chip inside every TV and monitor. When you plug in a cable, the console, PC or streaming stick reads it over a dedicated wire: the maker and model, every resolution and refresh rate the screen supports, its preferred mode, HDR and colour support, and the audio formats it can play.
The device compares that list with its own and picks the best mode they share. Problems start when the list is wrong or rewritten: a TV whose enhanced HDMI setting is off hands over a shorter list, soundbars, splitters, docks and KVM switches pass on their own edited version, and a device forced by hand to one mode ignores the list altogether. The EDID says nothing about the cable, which is why a cable too slow for the agreed mode shows sparkles or No signal.
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