Channel IDs
For channel IDs of active channels, they can be found from the share modal of the channel page. However, in order to find the channel ID of a suspended/deleted channel with only the username, we need to look at wayback archives.
2014 - 2018 Archives (HitchHiker Layout)
From 2014 - 2018, /user/
pages still resolved to the actual channel page, rather than returning 404, even if the channel was suspended/deleted. The page source of this page also contained the channel ID.
In the page source, we can Ctrl-F
for "CHANNEL_ID" to find the channel ID:
yt.setConfig('CHANNEL_ID', "UCe-YfgvFkhbX6tfZ34sAKig");
2010 - 2013 Archives (Beta & Cosmic Panda)
In early 2010, profile pictures switched from http://i4.ytimg.com/vi/kGA_keUyqSo/default.jpg
format to http://i1.ytimg.com/i/pAaoXljPxFhnHMg3dIqpeQ/1.jpg?v=8dd12c
The pAaoXljPxFhnHMg3dIqpeQ
value in the profile picture is actually the latest YouTube user ID (not to be confused with the old user IDs). the channel ID is UCpAaoXljPxFhnHMg3dIqpeQ
An example can be seen in this archive: