mastodon.social is one of the many independent Mastodon servers you can use to participate in the fediverse.
The original server operated by the Mastodon gGmbH non-profit

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@stickfog @Irishmasms Same. Though to be fair I'm only an occasional user... I was never on Instagram, so I don't care about replacing it, and I have not found #Pixelfed to be a suitable substitute for Facebook photos (or, for what it used to be).