How do I send a private message or DM or otherwise restrict my audience?

Mastodon provides several options to control post privacy, but there are several important things to know about private messaging on Mastodon: it may work differently than you expect, and messages aren't end-to-end encrypted.

Be aware that mentioning someone in a private message will include them in the conversation. This behaviour is different vs. Twitter/many other apps.

If you need to report an abusive user or post, use the Report functionality rather than a Mentioned people only post.

To control audience for a particular post, select Post Privacy options.

Options should be fairly self-explanatory, but there are some cosmetic and functional differences between the web app and the official Mastodon mobile app:

Post Privacy OptionDescriptionAvailable on desktopAvailable on mobile app
PublicThis post will be visible to anyone Yes Yes
Followers onlyThis post will be visible to your followers only Yes Yes
Mentioned people only
Only people I mention
Visible only to accounts which you mention in this post Yes Yes
UnlistedThis post will be visible to anyone, but is opted out of discovery features Yes No

Where do I find Post Privacy options?

Change post privacy button - Mastodon web UI

Post privacy options - Mastodon web UI