Alex Cranz (via John Gordon):
The first thing to understand is that the HDMI cable is not like the component, composite, or S-video cables you might have plugged into your TV in years past. All that mattered with those cables is that they were well made and had the right plugs. HDMI cables are more like USB or ethernet cables, however. There are different versions that look identical on the outside, but can grossly affect how much data you’re moving from point A to point B. You know how that old USB 2.0 cord slows down your external hard drive compared to a USB 3.0? HDMI is subject to the same kind of limitation—specifically, bandwidth.
There are, to date, seven different HDMI versions, starting with 1.0, which was introduced back in 2002, and currently ending with 2.1, which was only announced back in November of 2017.
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At this point, you might think you cracked the code, as if you could just go out, find an HDMI 2.0 or 2.1 cable, plug it in, and you’re good to go. Unfortunately, in 2012 HDMI pulled a truly bonehead move and essentially forbid anyone from actually saying what standards their cables support.
Update (2018-06-23): Ashley Bischoff:
And I gather that compatibility is less of a concern than the author makes it out to be.
This comment from spoonTRex seems to sum things up decently.