Collections can be Private. This is a PRO feature. The owner of the Collection can switch a Collection from Public to Private anytime. If the owner is no longer PRO, the Collection will remain private, but updating it will make it public.

A Private Collection has an obscure URL that cannot be guessed, so if anyone is seeing it it’s because they have access to it through CodePen (i.e. they are the owner) or the URL was shared with them.

Private Collections will not show up in any search on CodePen, except the owner searching their own work. We do our best to prevent search engines from indexing Private content, but we cannot ultimately control them and since the URL for a Private Collection is viewable it’s possible for a bot to see them.

You can also put Private Pens within Private Collections, and the behavior is a bit different than with Pub

• In a Public Collection, only you can see private things. They’re invisible to everyone else.
• In a Private Collection, all of the items are visible to anyone who has a link to the Collection, even Private Pens. This enables you to share a Collection of private work with a client or employer without making it visible to the general public. Remember that no one can see your private Collection unless you give them a link to it, so it won’t be visible anywhere on your public profile.