Puma
Puma: A free, open-source Ruby server with concurrency, clustering, SSL, and restart controls. Ranked #32 of 36 in Web Server Software by our editors (5.8/10); pricing: Free plan; best for ruby web applications.
At a glance
- Editor score5.8 / 10
- PricingFree plan
- Best forRuby web applications
- Free planYes
- Paid fromFree
- HTTP/3 supportNo
- Founded2011
- Facts checked20 Sep 2026
Where it wins
- Multithreaded handling with configurable thread pools
- Cluster mode supports multiple worker processes
- Rails, Sinatra, Rack, and systemd integrations
Where it doesn't
- HTTP/2 support is not included
- HTTP/3 support is not included
- Requires deployment with the application as self-hosted software
Our verdict on Puma
Puma is an open-source web server for Ruby and Rack applications, aimed at teams deploying Ruby services with their applications. It supports MRI Ruby, JRuby, Rubinius, and other Ruby implementations, and runs on Windows, Linux, and self-hosted environments. Its core request handling is multithreaded, with configurable thread pools, while cluster mode adds multiple worker processes. Puma is installed as a Ruby gem rather than operated as a hosted service.
Its strongest fit is the Ruby ecosystem. Integrations include Ruby on Rails, Sinatra, Rack, Bundler, Capistrano, and systemd, giving application teams familiar deployment and service-management connections. The server also supports SSL sockets, TCP and UNIX socket binding, request buffering, WebSockets through partial hijack, and systemd notification and monitoring. Hot and phased restarts help manage application changes, while the built-in control and status server provides operational visibility. Configurable plugins and server-wide hooks extend how the server can be managed around a Ruby application.
Puma is a practical choice for Ruby teams that want free, open-source infrastructure with concurrency, clustering, SSL, monitoring, and restart controls in one server. Its narrow focus is also its clearest boundary: it is designed for Ruby and Rack applications and is deployed with the application rather than consumed as a hosted platform. The published specifications show support for HTTP/1.1, WebSockets, and multiple Ruby implementations, but not HTTP/2 or HTTP/3. Teams building Ruby applications around Rails, Sinatra, or Rack should consider Puma; teams requiring HTTP/2 or HTTP/3 support should choose a server that provides those protocols.
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Puma pricing
Puma fact sheet
| Free plan | Yes |
|---|---|
| Paid from | Free |
| HTTP/2 support | No |
| HTTP/3 support | No |
| WebSocket support | Yes |
| Supported platforms | MRI Ruby, JRuby, Rubinius and other Ruby implementations |
| Plugin or module system | Yes |
| Windows support | Yes |
| Commercial support | Not verified |
| Deployment | Self-hosted |
| Platforms | Windows, Linux |
| Support | Community, Docs |
| Built for | Solo, Small business, Mid-market, Enterprise (editorial estimate) |
| Integrations | 6 integrations: Ruby on Rails, Sinatra, Rack, Bundler, Capistrano, systemd |
| Pricing | Free plan |
| Website | puma.io |
| Facts checked | 20 Sep 2026 |
Puma integrations
Puma lists 6 integrations on its own site.
- Ruby on Rails
- Sinatra
- Rack
- Bundler
- Capistrano
- systemd
Alternatives to Puma
- NGINXA focused self-hosted choice for serving, proxying, caching, and traffic control.9.4
- Apache HTTP ServerA mature, flexible choice for self-managed websites, applications, and HTTP traffic.9.3
- LiteSpeed Web ServerA capable Apache-compatible server for paid Linux hosting and control panels.8.9
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Featured on iTechGuides
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Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
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