HiveMQ

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

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

Realtime messaging service with presence, persistence and guaranteed delivery. The free plan includes 3m messages per month, 100 peak connections, and 100 peak channels.

Realtime messaging service, Pusher-compatible. Dev tier is limited to local development only and free with 100 concurrent connections, 1,000,000 broadcasts/month, unlimited client events, 32kb message size. ⬆️ Back to Top

Web Push Notifications - Free for upto 10k subscribers, unlimited push notifications, in-browser messaging

NATS.io as a service. Global, AWS, GCP, and Azure. Free forever with 4k msg size, 50 active connections, and 5GB of data per month.

SuprSend is a notification infrastructure that streamlines your product notifications with an API-first approach. Create and deliver transactional, crons, and engagement notifications on multiple channels with a single notification API. In free plan you get 10,000 notifications per month, including

SMS Gateway for Android™ enables sending and receiving SMS messages through your devices using cloud routing. Completely free cloud service (with recommended notification for usage above 10,000 messages/day to maintain quality for all users).