OneSignal is a customer engagement platform that enables companies of all sizes to increase retention and revenue through lightning-fast, personalized messaging. OneSignal supports email, push notifications, in-app messaging, SMS, Apple's Live Activities, and other channels via Webhooks. The platform is fast and easy for Developers to set up, and features an intuitive interface so Marketers are empowered to send messages without additional developer time. In addition to offering critical integrations, OneSignal also features an open API to allow greater messaging flexibility.