knock.app

Realtime messaging service. Free for up to 20 simultaneous connections and 100,000 events/day

Swift, Kotlin, and React messaging at 1 million transactions each month. Transactions may contain multiple messages.

Send push notifications to your iOS and Android devices. Effortlessly integrate via API or Webhooks and maintain full control over your alerts. Free plan: 50 messages per day to 1 device and 1 application.

Communication infrastructure in 5 minutes. Free tier includes: 100 SMS and calls, 3000 Emails, Push, Slack, MS Teams, WhatsApp, and more.

Send and receive text messages using your Android phone as an SMS Gateway. Free to send and receive up to 200 messages per month.

Connect your MQTT devices to the Cloud Native IoT Messaging Broker. Free to connect up to 100 devices (no credit card required) forever.

Multi-channel notification infrastructure for developers with a prebuilt in-app inbox and no-code template editor. Free plan includes 10,000 messages/mo.

All-in-one Customer Engagement and Automation Tool (email, push, SMS, product tours, banners and more) for SaaS. Free for up to 1,000 active users per month.