Bandcamp Pro has a feature where a release can be marked as “private”, making it discoverable only to people who have the link. This is often used by artists to provide early access to new releases for supporters before the release is published publicly. In other cases, the release may remain private indefinitely and effectively function as a subscriber-only collector’s item.
 
Anyone who has the link can access the page and stream the album. I have found no evidence that private albums can be purchased or downloaded.
 
We should allow adding /private/ streaming-only Bandcamp URL relationships to releases and recordings. Currently, when trying to add such a link, the release editor reports: “This URL is not allowed for releases.” For recordings, it reports: “This URL is not allowed for recordings.”
 
Some examples:

• https://bandcamp.com/private/GP6H33T6?ecmid=642
• https://bandcamp.com/private/V8QW9SU2
• https://bandcamp.com/private/V8QW9SU2/track/her-halo-on-the-rivers-surface
• https://bandcamp.com/private/GP6H33T6/track/entering-phonopolis-city-4

 
The canonical URL that this release may use in the future is usually available in the page source, but I do not think we can use it yet, because the album may never be published at that URL.