How to subscribe to a YouTube channel's RSS feed.

YouTube frequently makes changes that make it harder to keep up with your subscribed channels, but RSS still works. The instructions for using it are wrong though, and have been wrong for an extremely long time. They're also hard to find. So here's how to do it.

1. Get an RSS client (eg. Thunderbird. The following instructions will assume you're using Thunderbird but should be basically applicable to any feed reader).
2. Create one or more folders under "Feeds" to categorise your subscriptions. Or don't.
3. Right-click a folder (or "Feeds") and click "subscribe".
4. Under "Feed URL" paste "https://www.youtube.com/feeds/videos.xml?channel_id=" (without the quotation marks).
5. Open your web browser and find a channel you want to subscribe to.
6. If the URL contains the name of the channel (eg. https://www.youtube.com/user/Wallsy) then:
1. Open one of that channel's videos and then click the channel name under the video to return to the channel page. This time the URL should be different.
7. If the URL contains a string of gibberish (eg. https://www.youtube.com/channel/UCJpPXZwyo0fgu3h94R3P5pA), copy that gibberish.
8. Switch back to Thunderbird and paste the gibberish from the channel URL at the end eg. https://www.youtube.com/feeds/videos.xml?channel_id=UCJpPXZwyo0fgu3h94R3P5pA
9. Click "Add". Links to the latest videos from that channel should now be retrieved. You can set it to check for more videos automatically or just whenever you click the "Get Messages" button.