When creating a group, the creator selects a visibility setting that determines whether the group’s message archive is public (viewable by anyone who has the group's URL) or private (viewable only by members of the group).

After a group is created, a public archive can be changed to a private one, but a private archive cannot be changed to a public one. That is, if the group has a “publicly viewable messages” visibility setting, you can change it to a “private messages” setting—for example, if you changed your mind about the public visibility of the group’s message archive. But you cannot later change it back to a “publicly viewable messages” setting. All you can change is whether the group is listed in the public directory of groups on Groups.io.

Note: During the time when an archive is publicly viewable, web search engines might find and cache the content of some messages (that is, group messages could appear in the results of a web search). If the archive is later changed to a “private messages” setting, that cached content will still be available until it is purged by search engines when they discover that the content is no longer visible from the original page.