The short explanation
EDID stands for Extended Display Identification Data. When you switch on a player, console or streaming box, it does not magically know what your screen can do. It asks. The display answers with a small block of data — the EDID — that lists its name, its resolutions, its refresh rates, its color and HDR capabilities and its audio formats.
The source reads that list and picks the best combination both sides claim to support. That single exchange decides whether you get 4K120 or 1080p60, HDR or SDR, Atmos or stereo. It happens in under a second and you never see it.
Where you run into it
In a simple source-to-TV connection this works invisibly. Problems start as soon as there is something in between: an AV receiver, a soundbar, a switch, a long cable. Each device may pass the EDID through, rewrite it, or replace it with its own. What finally reaches the source can be very different from what your display actually advertises.
That is the cause behind a surprising share of HDMI complaints. No 4K120 even though every box says 4K120. No Dolby Vision on one input but fine on another. Atmos disappearing when you turn the projector off. The hardware is capable; the EDID that reached the source simply did not say so.
How the DR HDMI 8K handles it
The DR HDMI 8K sits between the source and the rest of the chain and takes over that exchange. It can show you the EDID the sink is advertising and the EDID the source is actually reading, side by side. It can copy the sink EDID unchanged, replace it with one of 100 stored tables (10 custom slots and 90 predefined), or copy it and change individual capabilities before passing it on.
That turns EDID from something invisible into something you can read, change and test one step at a time.
Want to test your own HDMI chain?
The DR HDMI 8K is sold through the HDFury.eu web shop.