Setting the redirect URL
The role of the single redirect URI on a developer app, the exact-match rule, separating environments, changing it, and common errors.
Creating a new app
How to register a developer app in a business account: the fields, how the credentials are shown, what you can do afterwards, and common stumbling points.
What is application registration
Explains the concept of ReceiptRoller application registration. Registering an app as an OAuth client issues a client ID, secret, and redirect URI, letting you start API and Webhook integrations.
Your first API call: from app registration to listing transactions
Get a token with the OAuth authorization code flow and PKCE, confirm the business account, list its transactions, and refresh the token.
API Authentication Guide
How to authenticate with the OAuth 2.0 authorization code flow: authorize parameters, the consent screen, token exchange and revocation, errors and scopes.
Managing the client ID and client secret
Where to find the client ID and client secret, how to store them, regenerating the secret after a suspected leak, and running several environments.
Cannot obtain a token (authentication error)
How to narrow down a 400 or 401 from the token endpoint, with the fix for each error and error_description, including invalid_client and invalid_grant.