Courier's push API can be used to deliver simple one-time push notifications to Android or iOS systems, providing an effective way to inform users about changes to a system, new messages, or in-app content. Push notifications are an important medium of modern communication, allowing for durable and efficient information delivery through mobile devices, where response times are measured in seconds. Unlike other types of push notifications, mobile pushes have a separate pipeline for generating, queuing, and distributing individual pushes, and are sent to users through a specific provider's service. Courier supports various push providers, including Firebase Cloud Messaging, Apple Push Notification Service, and OneSignal, offering customization options and integration with adjacent tools in the developer's stack.