Notion API turns Notion into a programmable workspace: read and write pages, query and filter databases, manipulate block trees. The most common indie use case is treating Notion as a headless CMS — store blog posts, changelogs, or knowledge base entries in a database, and have your frontend pull and render via API.

Authentication comes in two flavors. Internal integrations are zero-friction for personal use — generate a token and go, no OAuth dance. Public integrations follow standard OAuth and are suitable for app-marketplace distribution. Either way, the integration must be explicitly shared with the target page or database — that's Notion's permission model.

The block model is the heart of Notion's data shape: every page is a container of blocks, and blocks can be paragraphs, headings, lists, code, child databases, and so on. Reading a page usually means fetching its metadata first, then paginating through its block tree. Rate limit averages ~3 req/s, so bulk syncs need careful pacing. A handful of property types (rollups, formulas, relations) are read-only via API; writes go through upstream fields or the UI.