Kamal
Free, open-source (MIT) Docker deploy tool from 37signals.
Dev Hosting
What you get
Deploy containerized web apps to any servers, cloud or bare metal, with zero-downtime deploys via kamal-proxy; the tool 37signals uses to run HEY and its other apps.
How to get it
Install the kamal gem or run it from Docker, following kamal-deploy.org.
What it requires
Servers you can SSH into and a container registry.
The catch
Needs Linux and Docker familiarity; you manage the servers, which you pay for separately.
From the official page · checked Nov 1, 2026