Someone the account follows who also talks with it. Both sides need to have replied to, quoted, mentioned or reposted the other in recent public posts. X only lets the tool see who an account follows, not every follower, so talking back is what shows the tie goes both ways.
No. The tool only reads public posts and public follow lists, so there is nothing to log in to and nothing to authorise. It never touches your X account.
Yes. It works for any public X account, so you can check a friend, a creator you follow, or a brand. Private accounts cannot be read.
The tool reads a few hundred recent public posts, so older conversations drop off. It cannot see likes, direct messages or anything from private accounts, and someone who only mentions you without replying, quoting or reposting may not be found. For accounts that follow thousands of people, only the first couple of thousand follows are checked. You can take anyone off the list and the next mutual moves up.
The X Interaction Circle shows up to 50 people an account interacts with, including one-way ties. Top Mutuals only keeps people the account follows who also talk back, and puts the top five on a card.
Yes. It is completely free, with no sign-up, no watermark on the PNG apart from a small socialjj.com credit, and no limit on how many times you use it.