Visibility

The default. The share URL is not listed anywhere, is not linked from any public page, and the artifact page carries a noindex directive so search engines do not add it to their index.

It is not access control. If the URL is forwarded, pasted into a shared channel, or captured from a browser history, whoever has it can open the artifact. Treat an unlisted link the way you would treat an unlocked door in a building nobody knows the address of.

Available on Pro. A private artifact only renders for the account that owns it. Sending the URL to a colleague does not give them access.

Private is the right setting for a document you want stored and rendered but not distributed: a draft, an internal record, something mid-redaction.

Ask one question: if this URL ended up somewhere you did not send it, would that be a problem? If yes, unlisted is not enough, and the answer is either private visibility or removing the sensitive content before publishing.

Sandboxing and noindex protect the viewer and keep the page out of search. Neither protects the content from someone who has the link.