Asking the registration desk, carefully, and only a few desks
Socialscan checks whether a username or an email looks available, taken, or invalid on a small set of major platforms. It is a library and a command-line tool, under the Mozilla Public Licence 2.0. The platform list is short on purpose, and it changes between versions. Releases this course looked at have included names in the family of Instagram, X (Twitter), GitHub, Tumblr, and Last.fm. Your installed --help is the list. This paragraph is not the list. If a platform you care about is missing, socialscan did not check it. Silence is not a finding.
It talks to registration-style endpoints rather than loading a profile page. That is why, on the few sites it supports, it can be more precise than "did this URL 404?" checkers, and why it sits closer to Holehe than to Sherlock on the risk spectrum. You are not reading a shopfront. You are asking a signup desk whether the name is still for sale.
Learn the three words and refuse to upgrade them:
- Available. The platform says it would let someone register this identifier. Nobody in this course is going to register it as a stunt against a real brand.
- Taken, or unavailable. The platform says the identifier is in use, reserved, or otherwise not open. That is a registration answer. It is not a profile URL, a display name, a photo, or an identity.
- Invalid. The platform rejects the format. Too long, wrong characters, or otherwise not a name it will even consider.
"Taken" does not introduce you to the account. It does not mean the account is active. It does not mean a human, rather than a brand or a reserved word, holds it. Deleted accounts often keep the name taken. admin is taken everywhere and belongs to nobody you are looking for.
Sherlock asks whether a shopfront seems to exist. Socialscan asks whether the name is still on the shelf. People mix those questions up, and then they write the wrong sentence in the case file.