I know I can use an HDMI source like a Raspberry Pi and a small screen for HDMI and could twist copper cable together and measure continuity through them to narrow down which is which but I’m wondering if there is an easier way. Maybe something I connect to either end?
You’re question sounds like you are running the wires. They make numbered stickers specifically for marking long pulls of wire so you don’t have to test them. Just wrap a number around both ends and voila. https://www.amazon.com/Gardner-Bender-42-029-Booklet-Identification/dp/B000VZM37C
Instead of buying sheets of labels with numbers printed on for $12 you can get an actual label maker for like $15-$40 (or way more depending on how fancy you want to get)
Then you can label the wires with things like “living room cat5” instead of a cryptic “6” that you will forget the meaning of 3 years from now. If you spend a bit more (and maybe the cheap ones can do this, I dunno, I have a $40 one fwiw) you can get label refills that have heatshrink instead of labels. This is SO MUCH better because you can put it on the cable, shrink it, and it stays on forever. Unlike labels, which in my experience fall off when you pull them through walls (or just for no reason at all) 80% of the time. Downside is the heatshrink can’t go over big connectors so if it’s a cable you’re not terminating like hdmi it’s not as viable but for cat5/6 runs, coax, speaker wire, fiber, etc where you’re most likely terminating the cables yourself it’s the best. And even with big goofy hdmi cables you can still just get large heat shrink that has a good shrink ratio and write on it with a sharpie
Very true if you are doing a lot of work like that. I was only suggesting the easiest method for what I assume would be a one time thing.