Great question! Since you're already familiar with web-based JWT refresh patterns, let's adapt those ideas to mobile apps—while accounting for mobile-specific constraints like background execution, secure storage, and offline behavior.

Core Approaches for Mobile Token Management #

1. Refresh Token + Access Token Pairing (Most Common) #

This is a refined take on web-based patterns, perfectly suited for mobile's longer gaps between user interactions:

• Initial Flow: When a user logs in, your backend returns two tokens:
  • Access Token: Short-lived (e.g., 15–30 minutes), used for all regular API requests.
  • Refresh Token: Long-lived (e.g., 7–30 days), stored securely on the device (iOS Keychain, Android EncryptedSharedPreferences—never plaintext storage!).
• Refresh Trigger:
  • Before making any API request, check if the Access Token is expired or nearing expiration (e.g., less than 2 minutes remaining).
  • If so, call a dedicated /refresh-token endpoint with the Refresh Token. The backend validates the Refresh Token, then returns a new Access Token (and optionally a new Refresh Token to extend the session).
  • Update your local stored tokens and proceed with the original API request.
• Benefit: Works even if the app is idle in the background for hours—no constant user interaction needed, and reduces exposure risk for long-lived tokens.

2. Backend-Driven Silent Refresh (Web-Aligned) #

Similar to your web approach, but optimized for mobile:

• Every time your app sends an API request with the JWT, the backend checks the exp claim.
• If the token falls within a "refresh window" (e.g., 5 minutes of expiring), the backend includes a fresh JWT in the response headers or body.
• Your mobile app detects this new token, updates its secure storage, and uses it for subsequent requests.
• Caveat: Only works when the app is actively making requests. If the app is idle longer than the token's lifespan, this won't refresh automatically.

3. Background Refresh via Silent Push Notifications #

For apps needing to maintain sessions while idle in the background:

• Configure your backend to track token expiration times. When a user's token is approaching expiration (e.g., 1 hour left), send a silent push notification (iOS Silent Push, Android Data Push) to the device.
• The mobile app listens for this notification, wakes up briefly in the background, and triggers a token refresh request.
• Note: Mobile OSes have strict background limits (e.g., iOS's background task timeouts, Android's Doze mode). Use this as a supplementary mechanism, not the primary one.

4. Pre-emptive Refresh on App Foreground #

A simple, reliable fallback:

• Whenever the app is brought from the background to the foreground, check the Access Token's expiration.
• If it's expired or close to expiring, trigger a refresh immediately before the user interacts with the app.
• This ensures the user never hits an expired token during their session.

Critical Mobile-Specific Considerations #

• Secure Storage: Never store tokens in plaintext (e.g., Android SharedPreferences, iOS UserDefaults). Use platform-specific secure storage APIs to prevent token theft.
• Concurrency Handling: If multiple API requests detect an expired token at once, use a mutex or request queue to avoid duplicate refresh calls. Only one request triggers the refresh, others wait for the new token.
• Refresh Token Revocation: Implement a way to revoke Refresh Tokens (e.g., on logout, password change) to prevent misuse if the device is lost or stolen.
• Offline Fallback: If the app is offline when the token expires, queue API requests and refresh the token as soon as connectivity is restored.
• Graceful Expiry Handling: If the Refresh Token itself expires, guide the user through a seamless re-login flow (e.g., biometric authentication if enabled) instead of a full username/password prompt.

Content of the question comes from Stack Exchange, asked by zhaider