How Steam IDs work

Steam Community Database (SCDB) identifies an account by its SteamID64. Everything else is a display form until that number is known.

SteamID64

A SteamID64 is seventeen decimal digits. It is the durable identifier for a Steam account. SCDB stores and joins on that number. If a URL does not contain seventeen digits, it is not a SteamID64.

Vanity names

A custom profile URL such as /id/robinwalker is a nickname Steam will resolve for you. It is not an identifier. Two people can hold the same vanity at different times. SCDB will not store a vanity as if it were a key, and it will not look one up until Steam has turned it into a SteamID64.

SteamID2 and SteamID3

STEAM_X:Y:Z and [U:1:N] are the same account written differently. They are useful on a screen. They are not a second identifier. Convert them the same way everywhere, or you will join the wrong rows.

What SCDB will not do

A path that is not seventeen digits is not a profile. SCDB answers that with a 404, not a sign-in bounce and not a guess. Search still requires a Steam session. Signing in proves you control an account; it does not make a vanity into a key.