Shopify OAuth refresh token invalid_grant — What it means & how to fix it

Building Shopify apps with OAuth 2.0 often involves dealing with refresh token failures, notably the 'invalid_grant' error, which can disrupt various operations such as order processing and inventory syncs. These errors occur when a refresh token is invalid, expired, revoked, or stale after token rotation, and addressing them requires understanding the token lifecycle rather than treating them as network issues. Common causes include using outdated tokens after rotation, token expiration due to inactivity, unauthorized access following app uninstallation, and concurrency issues where multiple processes attempt token refresh simultaneously. To mitigate these problems, developers should ensure they are using the latest refresh tokens, verify the correctness of their refresh requests, and handle token refresh as an atomic operation to prevent concurrency bugs. If the token is genuinely invalid, re-authorization is necessary, and proactive measures such as refreshing tokens before expiration and maintaining a user-friendly re-authentication process are recommended. Additionally, tools like Nango offer solutions for managing OAuth token refreshes and handling lifecycle complexities, enabling developers to focus on building app features without being bogged down by token management challenges.