Definition
drive.file is a Google OAuth scope that grants an application access only to the specific Google Drive files the user opens with the app (typically through the Google file picker) or that the app itself creates. Everything else in the user's Drive stays invisible: the app cannot list, search, read, or modify any other file. It is the least-privilege way to build a Drive or Sheets integration.
Google classifies drive.file as a non-sensitive scope, and that matters in practice. The consent screen is the normal one-page approval with no "unverified app" warning, and the app does not have to pass Google's restricted-scope security assessment. Broader scopes like full Drive access or all-spreadsheets access trigger sensitive-scope review and scarier consent screens, which is why well-behaved integrations prefer drive.file plus a file picker.
How SheetLinkWP relates to drive.file Scope
SheetLink Forms' one-click Google Sheets connect (v1.12.0) requests only the drive.file scope. You click Connect Google, approve a standard consent screen, then use the Google file picker to select an existing spreadsheet or create a new one. From then on, SheetLink can see and write to exactly those spreadsheets - the ones you picked or it created for you - and nothing else in your Drive. Combined with the classic Apps Script webhook alternative (which uses no OAuth at all), neither Google Sheets connection method ever gets broad access to your Google account.