What does unlisted mean to Google

Google have 2 major products which offer "unlisted" options - Picasa Web Albums, and now Google Video.

Unlisted on Picasa Web Albums

Picasa Web Albums are created as either of

• Public (default) – This album will be listed in my public gallery
• Unlisted – Not listed in my public gallery (but may still be viewable if someone knows the album’s name)

At the moment there is no way to search within Public albums, though their URLs may show up in a search engine if a page links to them.

Unlisted albums started out needing just the album name to access them, which was guessable, but have now been changed so that you need the album's full URL - which incorporates an authkey parameter.  This has improved security considerably, since the URL is not guessable, but URLs can be forwarded to people they were not intended for, or indeed leak into search engines - Google is currently listing around 270 such URLs.

If you view unlisted albums from someone who you have added as a favorite within Picasa Web Albums, then your favorite screen in fact lists the "unlisted albums you have seen" from that user.

Unlisted albums are not private - to do that they would only be accessible to authorized viewers - requiring viewers to sign in before they can see the album.  A half-way house would be to password protect albums - this still suffers from the fact that passwords can be forwarded to other than the intended recipient, but at least passwords are not part of the URL, so don't appear in bookmarks and search engine discovered URLs, and if a viewing password gets into the wrong hands, you can change it, and just tell the rightful recipients the new password.

Picasa gives more explanation in their Picasa Web Albums FAQ. They suggest thinking of unlisted albums like unlisted phone numbers - anyone can see them, as long as they know the URL, but they are not listed in the directory.

Unlisted on Google Video

Google Video allows you to specify options for videos you upload:

• Public - your video will be included in search results
• Unlisted - your video will not be included in search results

Note that this is slightly different from the Picasa Web Albums case, since videos do have a way of searching them, and so this is explicitly about whether they are indexed by that search or not.

Video URLs, even the Public ones, include a long numeric docid, which effectively makes them unguessable.

The Google Help center has more to say on What are "unlisted" videos?

(More discussion on the Unlisted Videos at Google Video Adds "Unlisted" Option and Unlist Your Video.)