| Push notification | Anyone who granted permission, whether or not the app is open. | High. It arrives on the lock screen, uninvited. | Time-sensitive things the customer would want interrupting for: a delivery, a payment failure, a booking change. | Used for merchandising. Permission is withdrawn, and it is rarely granted twice. |
|---|
| In-app message | Only people already in a session. | Low. They are already there. | Onboarding, feature discovery, contextual offers, asking for the push opt-in at a sensible moment. | Shown on launch to everyone, every time, until it is dismissed reflexively. |
|---|
| Message inbox | Anyone with the app, whenever they choose to look. | None. The customer opens it. | Content with a shelf life: offers, statements, service updates worth keeping. | Nothing tells the customer it is there, so nobody opens it and the channel is assumed not to work. |
|---|
| App behavioral events | Not a message — the input that makes the others relevant. | None. | Triggering journeys on real app behavior rather than on email engagement. | Instrumented after the messaging is built, so the first campaigns run blind and set expectations low. |
|---|
| SMS or WhatsApp | A phone number. No app required. See SMS and WhatsApp. | High, and it reaches people who never installed anything. | Reach beyond your app population, and conversational exchanges. | Treated as cheap push. It is a different channel with different consent obligations. |
|---|