I know YouTube will throw a video to an extremely slow archival hard disk where getting 720p requires waiting a few minutes for YT to (presumably) move it to some regular storage tier with reasonable write speeds. But I've never heard of there being rot on the actual data YT stores, and I imagine it's on the same policy as Drive files where they're globally redundant, or at least in two different DCs.

I believe the parent is referring to deleted content, not literal unintended data loss.

It's more about policy than physical existence.

I have yet to see a definitive answer re true originals being kept vs iterations of transcodes as the preferred codec changes.

Or similar questions about deleted videos getting flagged vs scrubbed, etc.

Or who might ever have access to originals in either case.

Neil Cicierega's Ariel Needs Legs somewhat infamously had the audio corrupted on its YouTube upload over time: https://www.youtube.com/watch?v=_nH6ya5g2-s

It actually seems better from when I last looked at it, but you can you still hear skipping and audio jitter around spots like at 0:18. I've seen similar behavior on Twitter video uploads over the last few years.

I've seen video corruption myself on this video: https://youtu.be/XmWgskZFkh4. It's fixed now but there were glitches in the video and audio for a couple of years but somehow got fixed.

Music on YouTube is probably a bad example because it's subject to a lot of weird licensing restrictions and copyright claims.

Yes but is that reason to delete the metadata as well?

It is, which is tragic when trying to preserve favorites and all trace is gone (including titles.)

I'll intentionally duplicate playlist entries (two different uploaders) as a buffer against rot.