A simple, fast, multi-threaded, and highly parallel HTTP 1.1 server for Ruby/Rack applications.
Puma is a Ruby web server built for parallelism, designed to serve Rack applications with high performance. It uses a multi-threaded and multi-process architecture to handle more requests efficiently, making it the default server for Ruby on Rails. It solves the need for a fast, reliable, and scalable server in Ruby web development.
Ruby developers building web applications with frameworks like Rails or Sinatra who need a high-performance, production-ready web server. It's also suitable for DevOps engineers deploying Ruby applications in self-hosted or cloud environments.
Developers choose Puma for its battle-tested reliability, built-in parallelism, and seamless integration with Ruby ecosystems. Its ability to run standalone with SSL and support zero-downtime restarts makes it a robust alternative to other Ruby servers.
A Ruby/Rack web server built for parallelism
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Uses multi-threaded and multi-process architecture to handle concurrent requests efficiently, with cluster mode reducing memory via copy-on-write for better throughput.
Inherits a robust HTTP parser from Mongrel with over 15 years of production use, making it the default and most popular server for Ruby on Rails.
Includes built-in SSL support, zero-downtime rolling restarts, and a request bufferer, allowing deployment without a reverse proxy and reducing infrastructure overhead.
Offers extensive setup via CLI, environment variables, or config files with lifecycle hooks, plus a control server for runtime management and monitoring.
Lacks seamless restarts and cluster mode support on JRuby and Windows, and has known issues with Kubernetes pod shutdowns, limiting deployment flexibility.
Advanced features like thread pool tuning require careful setup to avoid resource exhaustion; misconfigured thread counts can lead to GVL contention on MRI or system overload.
Requires OpenSSL development files for SSL functionality; if missing, SSL connections are disabled, which can be a barrier in restricted or minimal environments.