Cloud accounts · Custom Google sign-in credentials
What are custom sign-in credentials, and when do I need them?
Short answer: A Client ID and Client Secret you create in Google's console so Google treats you as the app's owner. You only need them if Google shows "This app is blocked"; otherwise leave the fields blank and the built-in defaults are used.
They're a Client ID and Client Secret you create in Google's own console, so Google sees you as the app's owner. You only need them if Google blocks the normal sign-in — usually with a "This app is blocked" page — which happens most with work and school accounts.
Leave both fields blank to use the built-in defaults, which work for most personal Google Drive accounts. If you do create your own, they only work for the accounts you sign in with, so you stay in control of your own data. The fields are under Advanced — custom sign-in credentials in the Add Account sheet.
See creating them.