SteamID
Bulk mutual Friends finder
Paste any data that contains, SteamID , Steam3 , 64bit steam community below and hit submit!
SteamID will then look through its friends history of billions of records to locate matches between all inputs
More information about bulk mutual friends finder
The bulk mutual friends list is more so designed for server admins who have griefers come back consistently that may share the same friends, For example in the game Rust.The idea is you enter multiple SteamID64 , SteamID or Steam3 in the box and click the button, SteamID then runs through its friends list database (Mix of current and historic) and then finds the friends that all of the accounts you submitted have in common.
If you enter 4 profiles and have results come back it means that the friend shown appears in all 4 of the inputted users friends list or did at one point in time.