The default Mastodon search only returns results for posts that have federated with your server and include a hashtag. Mastodon supports ElasticSearch/Full-text search. When enabled, users on a Mastodon server can perform full-text searches for:
- their own statuses
- their mentions
- their favourites
- their bookmarks
- public statuses from accounts that opt-in to have their statuses indexed in search
- accounts (display name, usernames and bios)
This can be handy but requires a significant amount of extra server resources, so this feature is optional. On Masto.host, ElasticSearch is available as a paid add-on.