As of May 2020:
YouTube limits access to videos that are neither illegal, nor violate their own Terms and Conditions or Community Guidelines.
"Limited state" videos are placed behind a warning message, cannot be shared, monetized or easily found, and have likes, comments, view counts and suggested videos disabled.
altCensored.com is an unbiased community catalog of 40542 such videos, including those removed by YouTube or self-censored. Of 5550 monitored channels, 729 have been deleted and 1596 are being archived in case of deletion.