Is it Safe to Store an Auth Token in a Static Singleton on iOS?

Below is some guidance based on Apple’s recommendations for managing tokens:

Token Lifetime Matters

Tokens are generally considered safe when they have a short lifetime—typically a couple of minutes for a one‑off request or around 20 minutes for a long‑running process. Using a token with a longer lifetime than necessary can increase risk if it remains in memory too long. For some inherently safe GET requests (with scoped access) and specific resources, longer lifetimes (up to six months) are permitted, but those are exceptional cases.

In-Memory and Singleton Storage

It’s common to hold an authentication token in a singleton (or static variable) to enable quick access across your app. However, you must ensure that:

• The token’s lifetime is kept as short as practical to limit exposure.
• You have a strategy in place to rotate or refresh the token frequently.
• You’re not sharing the sensitive authentication state globally beyond what is necessary.

Storing a token in a global or static variable per se is not a problem, as long as the token is short‑lived and automatically refreshed if needed.

Using the Keychain as a Fallback

Storing the token in the Keychain is a good practice for persistent storage across app launches. You can retrieve it from the Keychain at startup and then keep it in memory for quick access during the session. This dual strategy is acceptable provided you’re careful with how long the token remains in memory. Always ensure your token isn’t kept in memory longer than its safe lifetime.

Final Thoughts

There is no inherent problem with using a singleton or static variable for your auth token if:

• You follow best practices on token lifetime
• You refresh the token as needed
• You ensure that you’re not exposing the token unnecessarily

If these security considerations are met, then using an in‑memory token for the duration of an operation is acceptable, but always weigh this convenience against potential security risks.

By following these practices, you can safely use a global variable for your token while also having a Keychain backup in case the in‑memory value is lost.