Notion API, Getting Invalid_Grant when trying to generate authorization token

Try removing the redirecturi from both the authorize call and the token exchange. The accepted answer reports that dropping redirecturi from both steps returned a success response from the server. So the authorize URL becomes just clientid and responsetype=code, and the token POST carries only granttype and code. If you do pass a redirecturi, it must be byte-identical in both calls and match what is registered on the integration settings page.

Context: Stack Overflow question (score 8, has accepted answer): After creating a Notion integration and completing the browser authorize step, exchanging the interim code at the Notion token endpoint returns {"error": "invalidgrant"}. The token request posts granttype=authorizationcode with the code and a redirecturi to https://api.notion.com/v1/oauth/token.

Stack Overflow question (score 8, has accepted answer): After creating a Notion integration and completing the browser authorize step, exchanging the interim code at the Notion token endpoint returns {"error": "invalidgrant"}. The token request posts granttype=authorizationcode with the code and a redirecturi to https://api.notion.com/v1/oauth/token. Resolved: Try removing the redirecturi from both the authorize call and the token exchange. The accepted answer reports that dropping redirecturi from both steps returned a success response from the server. So the authorize URL becomes just clientid and responsetype=code, and the token POST carries only granttype and code. If you do pass a redirecturi, it must be byte-identical in both calls and match what is registered on the integration settings page. Source: https://stackoverflow.com/questions/67782515/notion-api-getting-invalid-grant-when-trying-to-generate-authorization-token