Definition
The Google Sheets API is a RESTful web service that lets your application read, write, and format spreadsheet data over HTTPS. It exposes endpoints to append rows, update cells, create sheets, apply formatting, and run batch operations. To call it, your app authenticates with OAuth 2.0, obtains an access token, and then hits endpoints like spreadsheets.values.append. It is the standard path for desktop and mobile apps that need to treat a Sheet as a database.
The tradeoff is operational complexity. You must store OAuth refresh tokens, handle token expiration, respect per-user and per-project quota limits (currently 300 read or write requests per minute per project), and go through Google's OAuth verification for apps that want production-scale access.
How SheetLinkWP relates to Google Sheets API
SheetLink Forms does not use the Google Sheets API directly. Instead, it uses an Apps Script web app that the site owner deploys inside their own Google account. This design sidesteps OAuth complexity, quota sharing, and Google's app-verification process - and crucially keeps your data in your account. Customers with advanced needs (e.g., reading data back from Sheets in the WordPress admin) can still choose to connect via the API using the Two-Way Sync add-on, but the default form-to-Sheets path is intentionally the simpler Apps Script route.