Open the Maigret project first
Maigret is the GitHub tool from the video. Start from the project page, then use it to review your own public username footprint.
What it does
Maigret checks a username against many websites and finds public accounts that may use the same name.
The result is not proof of identity and can include false positives, so treat it as a privacy self-check.
Suggested use
Search your own common usernames and see which old accounts are still public.
Rename, delete, or lock down accounts you do not want connected.
If you are learning OSINT, only use accounts you own or have permission to check.