Notion OAuth invalid_grant from redirect_uri mismatch between the two calls

If Notion returns invalidgrant on the OAuth code exchange, compare the redirecturi sent in the authorize call with the one in the token call. Make them identical, or omit the parameter from both calls entirely, and the exchange will go through.

Context: Stack Overflow #67782515 (accepted answer, 13 votes): the asker completed the Notion OAuth authorize step fine but got invalidgrant when exchanging the code at /v1/oauth/token. The accepted answer found the mismatch: the authorize URL and the token request disagreed on redirecturi. Removing the redirect parameter from both calls, so neither call sent it, made the exchange succeed. Notion validates that the two calls agree on the value.

Source: Stack Overflow #67782515 (accepted answer, 13 votes): the asker completed the Notion OAuth authorize step fine but got invalidgrant when exchanging the code at /v1/oauth/token. The accepted answer found the mismatch: the authorize URL and the token request disagreed on redirecturi. Removing the redirect parameter from both calls, so neither call sent it, made the exchange succeed. Notion validates that the two calls agree on the value.

Verified resolution: If Notion returns invalidgrant on the OAuth code exchange, compare the redirecturi sent in the authorize call with the one in the token call. Make them identical, or omit the parameter from both calls entirely, and the exchange will go through.

Source URL: https://stackoverflow.com/questions/67782515/notion-api-getting-invalid-grant-when-trying-to-generate-authorization-token