Awesome

WEBrick - WEBrick is an HTTP server toolkit that can be configured as an HTTPS server, a proxy server, and a virtual-host server. It is now part of Ruby standard library for Ruby 1.9.3.
FCGI
CGI - The Common Gateway Interface (CGI) is a simple protocol for passing an HTTP request from a web server to a standalone program, and returning the output to the web browser.
SCGI
Thin - Tiny, fast & funny HTTP server. Glues together 3 of the best Ruby libraries: The Mongrel parser, Event Machine network I/O library and Rack, a minimal interface between webservers and Ruby frameworks.
LiteSpeed - LiteSpeed Web Server (LSWS) is a high-performance Apache drop-in replacement, a commercial web server.

These web servers include Rack handlers in their distributions:

net-http-server - A pure and small Ruby HTTP server.
Rouge - minimal and fast HTTP 1.1 server for Rack applications, powered by EventMachine, Ryan Dahl's http-parser(https://github.com/joyent/http-parser) and Rack::Builder.
Ebb - A small and fast web server specifically for hosting dynamic web applications.
Fuzed - An integrated replacement for Mongrel+Revproxy systems in erlang.
GlassFish v3 - An open-source application server project started by Sun Microsystems for the Java EE platform and now sponsored by Oracle Corporation.
Phusion Passenger - A web server and application server, designed to be fast, robust and lightweight. Supports Ruby, Python, Node.js and Meteor, and is being used by high-profile companies such as Apple, Pixar, New York Times, AirBnB, Juniper etc as well as over 350.000 websites. Phusion Passenger 5 (codename "Raptor") has an innovative and optimized HTTP engine, making it up to 4x faster than Unicorn, up to 2x faster than Puma and up to 2x faster than Torquebox.
Puma - A simple, fast, threaded, and highly concurrent HTTP 1.1 server writtern in Ruby.
Reel - A fast, non-blocking "evented" web server written in Ruby. You'll need reel-rack, a Rack adapter for Reel. Reel uses Celluloid, an Actor-based concurrent object framework for Ruby. When you create new instances of a class, they're actually concurrent objects, each running
- Reel::DSL - Minimalist Reel CRUD/WS/SSE endpoint routing. Supports URI-based HTTP/S requests, and Web Sockets & Server Sent Events. Influenced by Angelo and Sinatra.
- Angelo - Sinatra-like DSL for Reel that supports WebSockets and SSE in their own thread, called "cells" (or actors). Angelo uses Celluloid, Celluloid::IO. Angelo replaces Sinatra::Synchrony which is a very small extension for Sinatra Powered by EventMachine and EM-Synchrony that dramatically improves the concurrency of your web application.
Unicorn - Rack HTTP server for fast clients and Unix. Mostly wriiten in pure Ruby. Provides unicorn - a rackup-like command to launch the Unicorn HTTP server (it uses Rack::Builder DSL) and unicorn_rails - a script/server-like command to launch the Unicorn HTTP server.
unixrack - A ruby RACK webserver only for unix using the old unix style. (~500 LOC).
uWSGI - uWSGI application server container written in Python. Supports Python (WSGI), Ruby (Rack), Perl (PSGI), Lua (WSAPI), PHP (CGI), JVM (JWSGI), Mono (ASP.NET plugin), GO (GCCGO), CGI Scripts.
yahns - Sleepy, multi-threaded, non-blocking application server for Ruby.
YARS - A server for your (Rack) apps.
Goliath - A non-blocking Ruby web server framework. Bare metal performance, Rack API and middleware support, simple configuration, fully asynchronous processing, and readable and maintainable code. The framework is powered by an EventMachine reactor, a high-performance HTTP parser and Ruby 1.9+ runtime.
Mongrel - A HTTP library and web server written in Ruby. What makes Mongrel so fast is the careful use of an Ragel extension to provide fast, accurate HTTP 1.1 protocol parsing.
Mongrel2 - An application, language, and network architecture agnostic web server that focuses on web applications using modern browser technologies. Written in C.
Pow - Zero-config Rack server for Mac OS X. Have it serving your apps locally in under a minute. A Linux fork is availble here.
nack - A Rack server built on top of the Node.js HTTP server.
Gorack - A Go backed frontend webserver for Ruby's Rack applications, inspired by Node's nack.
Mizuno - Jetty-powered running shoes for JRuby/Rack. A Rack server for JRuby. It uses the embeddable Jetty Java servlet container. Mizuno also supports asynchronous request handling, via the Java Servlet 3.0 asynchronous processing mechanism.
TorqueBox - Ruby Web & Application Server built on JBoss and JRuby. TorqueBox goes beyond providing web-centric services (supporting Rails, Rack, Sinatra, etc), to also expose other enterprise-grade services to Ruby applications.
H2O - An optimized HTTP/1, HTTP/2 server. H2O supports Rack interface for MRuby.
trinidad - Run Rails or Rack applications within an embedded Apache Tomcat container.

Miscellaneous

Grack - GIt Smart HTTP Server Rack Implementation. This project aims to replace the builtin git-http-backend CGI handler distributed with C Git with a Rack application. This reason for doing this is to allow far more webservers to be able to handle Git smart http requests. Grack inspired git_http_backend.py and Git Web Access (ASP.NET/IIS).

Frameworks

Rum - A gRand Unified Mapper for Rack by Christian Neukirchen. Rum apps use a small DSL to set up the mappings. (~120 LOC)
Frack-MVC - A small example implementation of how to build a simple MVC style application from scratch. Check out the commit history to see how I implemented it step-by-step. This is the example code for the slide: Ruby MVC from scratch with Rack
Hobbit - A minimalistic microframework built on top of Rack (thanks to Rack::Builder). Hobbit is a DSL inspired by Sinatra. (~ 150 LOC).
- hobbit-contrib - Contributed Hobbit extensions. For examples: Hobbit::Environment, Hobbit::ErrorHandling, Hobbit::Filter, Hobbit::Mote - render using mote, Hobbit::Render, Hobbit::Session
- hat - Hobby Application Template. Combinded with i18n, rack-protection, sprockets, tilt, better_erros, rack-test, minitest and so on.
mruby-hibari - A Web application framework for Web servers that support mruby and Rack-based API. mruby-hibari currently supports the Web servers: ngx_mruby-enabled Nginx, mod_mruby-enabled Apache and h2o.
Cuba - Rum based microframework for web development. Integrates many templates via Tilt. Incredibly small, less than 200 lines of code.
- The Guide to Cuba - following this small book to build a Twitter clone called Frogger (work in progress).
Dolly - Minimal Ruby microframework inspired by Sinatra.
Nancy - Minimal Ruby microframework for web development inspired in Sinatra and Cuba (~150 LOC).
Rambutan - Ruby web microframework with Rails-ish controllers and routes.
NYNY - A (ridiculously) small and powerful web framework (~ 300 LOC). NYNY uses Journey for routing(Rail's router). A NYNY app is a Rack middleware, it can be used inside Sinatra, Rails, or any other Rack-based app.
Eldr - A lightweight, simple, modular and above all, clear framework without all the magic. (~500 LOC). Eldr uses Mustermann to build its Router.
rack-server-pages - Rack middleware and application for serving dynamic pages in very simple way. There are no controllers or models, just only views like a jsp, asp and php.
Serve - A small Rack-based web server that makes it easy to serve HTML, ERB, Haml, or a variety of template languages from any directory. Serve is meant to be a lightweight version of the Views part of the Rails MVC. Serve has full support for Rails-style partials and layouts.
RESTRack - RESTRack is a Rack-based MVC framework that makes it extremely easy to develop RESTful data services.
- RESTRack-Client - A library for interacting with RESTRack based services, although it provides a convenient API to any RESTful service.
- RESTRack-Balancer - A library for interacting with RESTful web services with automatic load balancing across a cluster.
- RESTRack-Splitter - A library for interacting with RESTful web services with automatic distribution across multiple nodes of a cluster.
jellyfish - Pico web framework for building API-centric web applications (~ 250 LOC).
junior - An MVC Web Framework.
u-web - A micro MVC framework based on Rack in a single file.
Kenji - A lightweight backend framework for Ruby.
cramp - A fully asynchronous realtime web application framework in Ruby. It is built on top of EventMachine.
Plezi - A framework for realtime, RESTful, websocket web apps. (M)VC desing, BYO models.
Brooklyn - Small web tool on top of Rack. No documentation.
Coset - A framework specifically for implementing RESTful Rack applications by Christian Neukirchen. Coset is introduced in the paper Introducing Rack.
Rango - An ultralightweight, ultracustomizable, ultracool web framework inspired by Django.
Pancake - Construct Rack stacks as mixins. Almost all key aspects of web frameworks are covered in Pancake as mixins to help you create your own re-usable Rack Stacks without worrying about the really low level plumbing.
Grape - An opinionated micro-framework for creating REST-like APIs in Ruby.
- Gris - A framework for building hypermedia API services using Grape, Roar and ActiveRecord.
Napa - Simple framework for building Rack based APIs using Grape, Roar and ActiveRecord.
It's designed to make it easy to quickly create and deploy new API services by providing generators, middlewares and a console similar to what you would expect from a Rails app.
Crep - A lightweight API framework designed to help you write clean, fast web services in Ruby. With an elegant and intuitive DSL inspired by RSpec, and with a nod to Grape, Crepe makes API design simple.
Praxis - A framework for both designing and implementing APIs.
Camping - A web framework which consistently stays at less than 4kB of code.
Espresso - Scalable Web Framework aimed at Speed and Simplicity.
Halcyon - A JSON Web Application Framework for developing lightweight applications interfaced via JSON-encoded HTTP requests.
Wee - A light-weight, very high-level and modern web-framework that makes Web engineering easy
Mack - A Ruby web application framework. It takes the best ideas from several frameworks, including Rails, Merb, and Ramaze.
Racket - A small MVC framework built on top of rack.
Merb - A web development framework for fast, simple, and powerful development.
Hanami - (formerly Lotus) A Ruby MVC web framework comprised of many micro-libraries. It has a simple, stable API, a minimal DSL.
- awesome-hanami - A collection of awesome Hanami Gems and projects.
Ramaze - A simple, light and modular open-source web application framework written in Ruby.
- ramaze-book - The official book for the Ramaze web framework.
Sin - A multi-app web-app DSL derived from Sinatra, riding on rack. Sin is a rebuild of sinatra, splitting up the classes into files and going for a reusable application class.
Gin - A small Ruby web framework, built on Rack, which borrows from Sinatra expressiveness, and targets larger applications.
Pakyow - An open-source framework for the modern web. Build web-based apps faster with a view-first development process that's friendly to everyone.
Scorched - Light-weight, DRY as a desert, web framework for Ruby. Simliar to Sinatra. Scorched is a true evolutionary enhancement of Sinatra, with more power, focus, and less clutter.
Rack::App - Bare bone minimalistic (masochistic) pico framework for building rack apps. Inspired by sinatra, grape and the pure use form of Rack.
Trailblazer - A high-level, modular architecture for Ruby framworks with domain and form objects, view models, twin decorators.
Sinatra - Classy web-development dressed in a DSL for quickly creating web applications in Ruby with minimal effort. Sinatra is not a framework, nor a MVC, it's a wrapper around Rack.
- sinatra-contrib - Collection of common Sinatra extensions.
- sinatra-receipes - Community contributed recipes and techniques for the Sinatra Web Framework.
- sinatra-book - A cookbook full of excellent tutorials and recipes for developing Sinatra web applications.
- Frameworks inspired by Sinatra on Wikipedia - e.g.: Ruby (Padrino, Nancy), PHP (Slim, deano), JavaScript (Express), CoffeeScript (Zappa), Python (Flask), Go (Martini, Goji), Scala (Finatra, Scaltra), Java (Spark), Haskell (Scotty), Bash (sh.inatra), Lua (Orbit, Mercury), Perl (Dancer)
padrino - Padrino is a full-stack ruby framework built upon Sinatra.
- padrino-contrib - Contributed plugins and utilities for Padrino Framework.
- padrino-recipes - A collection of padrino templates and plugins.
Rails - Ruby on Rails, is a MVC web application framework written in Ruby.
Volt - A reactive web framework where your Ruby runs on both server and client (via Opal). A framework for building data rich web applications shockingly fast. Instead of syncing data between the client and server via HTTP, Volt uses a persistent connection between the client and server. When data is updated on one client, it is updated in the database and any other listening clients (with almost no setup code needed). Volt apps share MVC and routes between client and server. Same Ruby code runs on the client and server! (Isomorphic App Development) Volt plans to integrate RethinkDB and RubyMotion.

Middlewares

Where you can find middlewares

Rack built-in middlewares:
- Rack::Builder - Implements a small DSL to iteratively construct Rack applications.
- Rack::BodyProxy -
- Rack::Cascade - Tries a request on several apps, and returns the first response that is not 404 or 405 (or in a list of configurable status codes).
- Rack::Chunked - Middleware that applies chunked transfer encoding to response bodies when the response does not include a Content-Length header.
- Rack::CommonLogger - For creating Apache-style logfiles.
- Rack::ConditionalGet - Middleware that enables conditional GET using If-None-Match and If-Modified-Since. The application should set either or both of the Last-Modified or Etag response headers according to RFC 2616
- Rack::Config - modifies the environment using the block given during initialization
- Rack::ContentLength - Sets the Content-Length header on responses with fixed-length bodies
- Rack::ContentType - Sets the Content-Type header on responses which don't have one
- Rack::ETag - Adds ETag header on all String bodies. ETags are used to validate cache.
- Rack::File - serves files below the root directory given, according to the path info of the Rack request. e.g. when Rack::File.new("/etc") is used, you can access 'passwd' file as http://localhost:9292/passwd
- Rack::Deflater - enables compression of http responses, currently supported compression algorithms: gzip, deflate, identy (no transformation)
- Rack::Directory - serves entries below the root given, according to the path info of the Rack request. If a directory is found, the file's contents will be presented in an html based index. If a file is found, the env will be passed to the specified app.
- Rack::ForwardRequest - gets caught by Rack::Recursive and redirects the current request to the app at url
- Rack::Handler - Handlers connect web servers with Rack. Rack includes Handlers for Thin, WEBrick, FastCGI, CGI, SCGI and LiteSpeed. Handlers usually are activated by calling MyHandler.run(myapp). A second optional hash can be passed to include server-specific configuration.
- Rack::Head - returns an empty body for all HEAD requests. It leaves all other requests unchanged.
- Rack::Lint - validates your application and the requests and responses according to the Rack spec
- Rack::Lock - locks every request inside a mutex, so that every request will effectively be executed synchronously
- Rack::Logger - Sets up rack.logger to write to rack.errors stream
- Rack::MethodOverride - Override HTTP verbs. Lets you use HTTP verbs such as PUT or DELETE in places where the client doesn't support it. The way this works is by letting the client do an HTTP POST request and set the X-HTTP-Method-Override header and set the value to the intended HTTP method (such as PATCH).
- Rack::Mime - Returns String with mime type if found
- Rack::NullLogger -
- Rack::Recursive - allows applications called down the chain to include data from other applications (by using rack['rack.recursive.include'][...] or raise a ForwardRequest to redirect internally
- Rack::Reloader - High performant source reloader
- Rack::Runtime - Sets an "X-Runtime" response header, indicating the response time of the request, in seconds
- Rack::Sendfile - The Sendfile middleware intercepts responses whose body is being served from a file and replaces it with a server specific X-Sendfile header. The web server is then responsible for writing the file contents to the client
- Rack::Server - Rack Server starter, used by rackup to start a rack server and use Rack::Builder to construct Rack applications.
- Rack::ShowException - for catching unhandled exceptions and presenting them in a nice and helpful way with clickable backtrace.
- Rack::ShowStatus catches all empty responses and replaces them
- Rack::Static - intercepts requests for static files (javascript files, images, stylesheets, etc) based on the url prefixes or route mappings passed in the options, and serves them using a Rack::File object. This allows a Rack stack to serve both static and dynamic content. `
- Rack::TempfileReaper - Middleware tracks and cleans Tempfiles created throughout a request (i.e. Rack::Multipart) Ideas/strategy based on posts by Eric Wong and Charles Oliver Nutter
- Rack::URLMap - takes a hash mapping urls or paths to apps, and dispatches accordingly. Support for HTTP/1.1 host names exists if the URLs start with http:// or https://. URLMap modifies the SCRIPT_NAME and PATH_INFO such that the part relevant for dispatch is in the SCRIPT_NAME, and the rest in the PATH_INFO. This should be taken care of when you need to reconstruct the URL in order to create links.
- Rack::Utils - contains a grab-bag of useful methods for writing web applications adopted from all kinds of Ruby libraries
- Rack::Multipart - A multipart form data parser, adapted from IOWA. Usually, Rack::Request#POST takes care of calling this.
- Rack::Request - which also provides query string parsing and multipart handling.
- Rack::Response - for convenient generation of HTTP replies and cookie handling.
- Rack::MockRequest and Rack::MockResponse- for efficient and quick testing of Rack application without real HTTP round-trips.
- Rack::Auth::Basic - implements HTTP Basic Authentication, as per RFC 2617
- Rack::Auth::Digest::MD5 implements the MD5 algorithm version of HTTP Digest Authentication, as per RFC 2617.
- Rack::Session::Cookie - provides simple cookie based session management. The session is a Ruby Hash stored as base64 encoded marshalled data set to :key (default: rack.session)
- Rack::Session::Pool - provides simple cookie based session management. Session data is stored in a hash held by @pool
- Rack::Session::Memcache - provides simple cookie based session management. Session data is stored in memcached
- Note that these are not middlewares: Rack::BodyProxy, Rack::Cascade, Rack::File, Rack::ForwardRequest, Rack::Handler, Rack::Mime, Rack::Server, Rack::URLMap, Rack::Utils, Rack::Multipart, Rack::Request, Rack::Response, Rack::MockRequest and Rack::MockResponse,
rack-contrib - Contributed Rack Middleware and Utilities. This package includes a variety of add-on components for Rack:
- Rack::AcceptFormat - Adds a format extension at the end of the URI when there is none, corresponding to the mime-type given in the Accept HTTP header.
- Rack::Access - Limits access based on IP address
- Rack::Backstage - Returns content of specified file if it exists, which makes it convenient for putting up maintenance pages.
- Rack::CSSHTTPRequest - Adds CSSHTTPRequest support by encoding responses as CSS for cross-site AJAX-style data loading
- Rack::Callbacks - Implements DSL for pure before/after filter like Middlewares.
- Rack::Config - Shared configuration for cooperative middleware.
- Rack::Cookies - Adds simple cookie jar hash to env
- Rack::Deflect - Helps protect against DoS attacks.
- Rack::Evil - Lets the rack application return a response to the client from any place.
- Rack::HostMeta - Configures /host-meta using a block
- Rack::JSONP - Adds JSON-P support by stripping out the callback param and padding the response with the appropriate callback format.
- Rack::LazyConditionalGet - Caches a global Last-Modified date and updates it each time there is a request that is not GET or HEAD.
- Rack::LighttpdScriptNameFix - Fixes how lighttpd sets the SCRIPT_NAME and PATH_INFO variables in certain configurations.
- Rack::Locale - Detects the client locale using the Accept-Language request header and sets a rack.locale variable in the environment.
- Rack::MailExceptions - Rescues exceptions raised from the app and sends a useful email with the exception, stacktrace, and contents of the environment.
- Rack::NestedParams - parses form params with subscripts (e.g., * "post[title]=Hello") into a nested/recursive Hash structure (based on Rails' implementation).
- Rack::NotFound - A default 404 application.
- Rack::PostBodyContentTypeParser - Adds support for JSON request bodies. The Rack parameter hash is populated by deserializing the JSON data provided in the request body when the Content-Type is application/json.
- Rack::Printout - Prints the environment and the response per request
- Rack::ProcTitle - Displays request information in process title ($0) for monitoring/inspection with ps(1).
- Rack::Profiler - Uses ruby-prof to measure request time.
- Rack::RelativeRedirect - Transforms relative paths in redirects to absolute URLs.
- Rack::ResponseCache - Caches responses to requests without query strings to Disk or a user provider Ruby object. Similar to Rails' page caching.
- Rack::ResponseHeaders - Manipulates response headers object at runtime
- Rack::Sendfile - Enables X-Sendfile support for bodies that can be served from file.
- Rack::Signals - Installs signal handlers that are safely processed after a request
- Rack::SimpleEndpoint - Creates simple endpoints with routing rules, similar to Sinatra actions
- Rack::StaticCache - Modifies the response headers to facilitiate client and proxy caching for static files that minimizes http requests and improves overall load times for second time visitors.
- Rack::TimeZone - Detects the client's timezone using JavaScript and sets a variable in Rack's environment with the offset from UTC.
- Rack::TryStatic - Tries to match request to a static file
List of Middleware on Rack's Wiki. Copied here (ver 2016/03/03):
- JSON-P
- Rack::Cache is suitable as a quick drop-in component to enable HTTP caching.
- Rack::ESI is a small (but still very useful!) subset of ESI (Edge Side Includes).
- CloudKit includes OpenIDFilter, OAuthFilter, and RESTful JSON storage
- Rack::Config - Shared configuration for cooperative middleware.
- Rack::OpenID provides a more HTTPish API around the ruby-openid library.
- Rack::Debug
- Rack::AbstractFormat
- Rack::RespondTo allows triggering different actions based on requested media type.
- Rack::SupportedMediaTypes specify an app's supported media types.
- Rack::AcceptMediaTypes determine the request's prefered media type.
- Rack::MultipartRelated parses multipart/related requests and rebuild a simple/merged parameters hash.
- Rack::Heartbeat Add a configurable heartbeat/health-check/ping url to your app
- Rack::Honeypot acts as a spam trap.
- Rack::GoogleAnalytics embeds Google Analytics tracking code.
- Rack::Embed embeds small images via the data-url (base64) if the browser supports it. This reduces http traffic.
- Warden General Rack Authentication Framework
- Rack::StaticFallback bounces or redirects requests to missing static files.
- Rack::Throttle provides logic for rate-limiting incoming HTTP requests to Rack applications.
- Rack::LinkedData implements Linked Data content negotiation.
- SimpleRouter
- Cylon Disallows application indexation by search engines except in production. Rack Middleware and Rails Engine.
- Slogger::Rack::RequestLogger if you want to log on Syslog.
- Rack::Batik::SVG transcodes SVG pictures to JPEG
- Rack::Referrals extracts referring search engine info
- Muster parses some or all of the query string in varying formats into hashes. Helps adding human friendly (not rack/rails nested) query string options to APIs and such.
- Moneta adds Rack::MonetaStore (places key/value store in env, support for per-request caching), Rack::MonetaCookies (allow Moneta to be used to store cookies) and Rack::MonetaRest (expose a key/value store via HTTP/REST)
- RouteDowncaser makes all routing in Rails case-insensitive.
- Rack::CanIUse checks if user agents support the HTML/CSS technologies used by your website using the CanIUse database.
- Rack::Attack A DSL for blocking & throttling abusive clients
- ChromeLogger A Ruby library that implements the Chrome Logger spec as Rack middleware
- Rack::DetectTor Detect Tor exit users
- Rack::RackTorBlock Block access to a rack application from any client accessing from the Tor network
- Rack::Turnout Easily put your Rack apps into maintenance mode
- Rack::CAS Simple CAS client authentication
- Rack::AcornCache Configurable HTTP proxy caching solution
Rubygems - Search the keywords rack or middleware

Rail's ActionController Middleware Stack

To see what middleware your Rails app is using, open it up in command line and run:

   rake middleware

You will see a big list of middleware classes that your current Rails app is using. A sample outout:

use ActionDispatch::Static
use Rack::Lock
use #<ActiveSupport::Cache::Strategy::LocalCache::Middleware:0x007f93ff6810d8>
use Rack::Runtime
use Rack::MethodOverride
use ActionDispatch::RequestId
use Rails::Rack::Logger
use ActionDispatch::ShowExceptions
use ActionDispatch::DebugExceptions
use BetterErrors::Middleware
use ActionDispatch::RemoteIp
use ActionDispatch::Reloader
use ActionDispatch::Callbacks
use ActiveRecord::ConnectionAdapters::ConnectionManagement
use ActiveRecord::QueryCache
use ActionDispatch::Cookies
use ActionDispatch::Session::CookieStore
use ActionDispatch::Flash
use ActionDispatch::ParamsParser
use ActionDispatch::Head
use Rack::ConditionalGet
use Rack::ETag
use ActionDispatch::BestStandardsSupport
use Warden::Manager
run MyApplication::Application.routes

Middlewares for Source Reloader

Rack::Reloader from Rack built-in middlewares - High performant source reloader
Shotgun - An automatic reloading version of the rackup command that's shipped with Rack.
rack-unreloader - A rack library that reloads application files when it detects changes, unloading constants defined in those files before reloading
guard-rack - Restart Rack when files change
ActionDispatch::Reloader from Rail's ActionController Middleware Stack - Provides prepare and cleanup callbacks, intended to assist with code reloading during development
rack-livereload - Bring in livereload.js into handy Rack middleware
guard-livereload - automatically reload your browser when 'view' files are modified

Middlewares for HTTP Routing

From Rack built-in middlewares:
- Rack::URLMap - to route to multiple applications inside the same process.
- Rack::Static - intercepts requests for static files (javascript files, images, stylesheets, etc) based on the url prefixes or route mappings passed in the options, and serves them using a Rack::File object. This allows a Rack stack to serve both static and dynamic content. `
rack-no-www - This piece of simple middlweware catches requests that begin with "www" and redirects them to the equivalent "non-www" address. For example, a request to "http://www.example.org" will be redirected to "http://example.org".
rack-routing - Map URL routes to Ruby methods
angus-router - A router for Rack applications.
rack-router - A simple router for rack apps. Requires Ruby 1.9+. (~ 200 LOC)
SimpleRouter - Small and simple standalone router, meant for use with Rack applications. Familiar Sinatra-like DSL for defining actions. Modular architecture.
Syro - Simple router for web applications inspired by Cuba. (~ 250 LOC)
Toro - Tree Oriented Routing
http_router - This is an HTTP router for use in either a web framework, or on it's own using Rack.
sinatra-router - A tiny vendorable router that makes it easy to try routes from a number of different modular Sinatra applications
sinatra-advanced-routes - Make Sinatra routes first class objects (extracted from BigBand).
Rack::Mount - A stackable dynamic tree based Rack router.
Lotus::Router - Rack compatible, lightweight and fast HTTP Router for Ruby and Lotus.
Pendragon - Provides an HTTP router for use in Rack and Padrino
Journey - A router for rails. Journey is a router. It routes requests.
Usher - Pure ruby general purpose router with interfaces for rails, rack, email or choose your own adventure
Roda - Routing Tree Web Framework Toolkit
Rack Reverse Proxy - This is a simple reverse proxy for Rack that pretty heavily rips off Rack Forwarder.
Rack::Rewrite - A rack middleware for defining and applying rewrite rules
Hanami::Router - Rack compatible, lightweight and fast HTTP Router for Ruby and Hanami.

Middlewares for Session Management

From Rack built-in middlewares:
- Rack::Session::Abstract - includes Rack::Session::Abstract::ID for implementing an id based sessioning service and Rack::Session::Abstract::SessionHash for lazily loading the session from store.
- Rack::Session::Cookie - provides simple cookie based session management. The session is a Ruby Hash stored as base64 encoded marshalled data set to :key (default: rack.session)
- Rack::Session::Pool - provides simple cookie based session management. Session data is stored in a hash held by @pool
- Rack::Session::Memcache - provides simple cookie based session management. Session data is stored in memcached
From Rail's ActionController Middleware Stack:
- ActionDispatch::Session::CookieStore - Uses the cookie based session store.
- ActionDispatch::Session::CacheStore - Uses the Rails cache based session store
- ActionDispatch::Session::MemCacheStore - Uses the memcached based session store.
- ActiveRecord::SessionStore - Uses the database based session store.
rack-deadline - A simple rack middleware that automatically clears sessions that have been open too long (by default, 1 day)
rack_session_access - provides rack middleware for 'rack.session' environment management
Moneta - Moneta provides a standard interface for interacting with various kinds of key/value stores. Moneta supports the well-known NoSQL and document based stores.
- Rack::Session::Moneta - is a Rack middleware to use Moneta for storing sessions
- Rack::MonetaCookies - is a Rack middleware which uses Moneta to store cookies
- ActionDispatch::Session::MonetaStore - is a Rails middleware to use Moneta for storing sessions

Middlewares for Caching

Rack::ETag from Rack built-in middlewares - Adds ETag header on all String bodies. ETags are used to validate cache.
rack-cache - A quick drop-in component to enable HTTP caching for Rack-based applications that produce freshness (Expires, Cache-Control) and/or validation (Last-Modified, ETag) information
Garner - A set of Rack middleware and cache helpers that implement various caching strategies.
rack-cache-smash - Rack middleware to cache bust every CSS and JS asset request
Rack::Cachely - Rack Middleware for working with the CachelyApp Page Cache Service, Cachely
Faraday Http Cache - A Faraday middleware that respects HTTP cache, by checking expiration and validation of the stored responses.
Rack::Worker - Rack middleware that implements the Worker Pattern. It processes GET requests with a worker backend and only serves them straight from a cache. While processing the request it serves empty HTTP 202 responses. Your web frontend is never blocked processing the request.
Moneta - Moneta provides a standard interface for interacting with various kinds of key/value stores. Moneta supports the well-known NoSQL and document based stores.
- Rack::MonetaStore - is a Rack middleware which places a Moneta store in the environment and enables per-request caching
- Rack::Cache::Moneta - provides meta and entity stores for Rack-Cache
- ActiveSupport::Cache::MonetaStore - is a Rails cache implementation which uses a Moneta store as backend
- Ramaze::Cache::Moneta - is integrated into the Ramaze project and allows Ramaze to use Moneta as caching store

Middlewares for Authentication

Rack::Auth::Basic and Rack::Auth::Digest from Rack built-in middlewares - HTTP Basic Authentication and HTTP Digest Authentication
Warden - General Rack Authentication Framework
Devise - A flexible authentication solution for Rails based on Warden. A complete MVC solution based on Rails engines
OmniAuth - A flexible authentication system utilizing Rack middleware
rack-oauth2 - OAuth 2.0 Server & Client Library. Both Bearer and MAC token type are supported.
Rack::OAuth2::Server - OAuth 2.0 Authorization Server as a Rack module. Supports Sinatra and Rails.
rack-openid - Provides a more HTTPish API around the ruby-openid library
rack-jwt-token-auth - JWT-based token authentication middleware for Rack.
Shield - Authentication protocol for use in your routing and model context (~ 110 LOC)
Heroku Bouncer - Rack middleware (implemented in Sinatra) that requires Heroku OAuth on all requests.
sinatra_auth_github - A sinatra extension that provides oauth authentication to github. See Scott Chacon's Minimal Sinatra GitHub Application for a demostration.
Rack::FacebookConnect - A Rack middleware for Facebook Connect authentication.
Rack::Cerberus - Rack middleware for form-based authentication. It works roughly like Basic HTTP authentication except that you can use options in order to style the authentication page.
hancock - An OpenID based Single Sign On server with a simple API, written in Sinatra
- hancock-client - A sinatra app and rack middleware piece for the hancock SSO server
ntlm-sso - Rack authentication module for single sign on via NTLM. Note this is not a middleware.
CASino - Ruby-based Single Sign-On solution supporting the CAS standard. Note this is not a middleware.
- CASinoApp - Ready to use CAS server based on CASino Rails Engine.
OmniAuth - A flexible authentication system utilizing Rack middleware.

Middlwares for Asset Pipeline

Sprockets - Sprockets is a Ruby library for compiling and serving web assets. It features declarative dependency management for JavaScript and CSS assets, as well as a powerful preprocessor pipeline that allows you to write assets in languages like CoffeeScript, Sass and SCSS.
rack-sprocketize - a piece of Rack Middleware which uses Sprockets to concatenate javascript files and then optionally compresses them.
rack-pack - A piece of Rack Middleware that packages and optionally compresses assets such as javascripts and stylesheets into single files.
Rack Pipeline - A rack middleware to serve javascript and stylesheet assets for ruby web applications
rack-coffee - Simple rack middleware for serving up CoffeeScript files as compiled javascript
rack-bundle - A Rack middleware for grouping Javascripts and stylesheets into one single file (styles are grouped by media type).
rack-zippy - A Rack middleware for serving static gzipped assets precompiled by the Rails (4.1 and earlier) asset pipeline into the public/assets directory.
Hork - Rack middleware for transparently compressing JavaScript and CSS assets with the YUI Compressor
Sinatra AssetPack - The most convenient way to manage your assets in Sinatra
rack-asset-compiler - Rack middleware that provides a generic interface for compiling static files, such as Sass or CoffeeScript files.
Rack::Cat - A Rack middleware to concatenate your assets (static, dynamic and remote) and serve javascripts and stylesheets faster.
Rack::Pack - for packaging assets such as javascripts and stylesheets into a single file.

Middlewares for Debugging or Profiling

From Rack built-in middlewares:
- Rack::ShowException - for catching unhandled exceptions and presenting them in a nice and helpful way with clickable backtrace.
- Rack::ShowStatus catches all empty responses and replaces them with a site explaining the error
- Rack::Runtime sets an "X-Runtime" response header, indicating the response time of the request, in seconds
From Rail's ActionController Middleware Stack:
- ActionDispatch::ShowExceptions - Rescues any exception returned by the application and calls an exceptions app that will wrap it in a format for the end user.
- ActionDispatch::DebugExceptions - Responsible for logging exceptions and showing a debugging page in case the request is local.
rack-webconsole - Rack-based interactive console (ana Rails console) in your web application's frontend. That means you can interact with your application's backend from within the browser itself!
rack-webconsole-pry - based on rack-webconsole, uses pry instead of ripl, supports colors.
PryRescue::Rack - pry-rescue is an implementation of "break on unhandled exception" for Ruby. Whenever an exception is raised, but not rescued, pry-rescue will automatically open Pry for you.
rack-bug - Rack::Bug adds a diagnostics toolbar to Rack apps. When enabled, it injects a floating div allowing exploration of logging, database queries, template rendering times, etc.
rack-debug - A middleware that provides a simple interface to ruby-debug. Helps debug apps running in Passenger
rack-insight - Rack::Insight adds a diagnostics toolbar to Rack apps. When enabled, it injects a floating div allowing exploration of logging, database queries, template rendering times, etc. Rack::Insight stores debugging info over many requests, incuding AJAX requests. Forked from rack-bug
racksh - Console for Rack based ruby web apps. It's like script/console in Rails (~ 100 LOC) or merb -i in Merb, but for any app built on Rack. Thanks to Rack::Test::Methods (from rack-test) and Ruby REPLs (pry and irb).
rack-monitor - Rack middleware for collecting run-time information for monitoring tools like Munin
Rack::PerftoolsProfiler - Middleware for profiling Rack-compatible apps using perftools.rb
Bugsnag - The Bugsnag Notifier for Ruby gives you instant notification of exceptions thrown from your Rails, Sinatra, Rack or plain Ruby app
Better Errors - Better Errors replaces the standard Rails error page with a much better and more useful error page. It is also usable outside of Rails in any Rack app as Rack middleware.
rack-mini-profiler - Middleware that displays speed badge for every html page. A simple but effective mini-profiler for .NET, Ruby, Go and Node.js. Introduced in Railscasts #368 MiniProfiler
New Relic RPM Ruby Agent - New Relic is a performance management system. It provides you with deep information about the performance of your Rails or Ruby application as it runs in production. When running in developer mode, the New Relic Ruby Agent acts as a Rack middleware that maps /newrelic to an application for showing detailed performance metrics on a page by page basis. Installed automatically in Rails applications
Airbrake::Rack::Middleware - Airbrake Rack middleware for Rails and Sinatra applications (or any other Rack-compliant app). Any errors raised by the upstream application will be delivered to Airbrake and re-raised.

Middlewares for Protection

rack-protection - This gem protects against typical web attacks. Prevented Attacks includes Cross Site Request Forgery, Cross Site Scripting, Clickjacking, Directory Traversal, Session Hijacking, IP Spoofing. Note: This project has been merged upstream to sinatra/sinatra.
rack-attack - Rack middleware for blocking & throttling abusive requests. It allows whitelisting, blacklisting, throttling, and tracking based on arbitrary properties of the request.
rack-block - A rack middleware for controlling accesses by search bot or not, remote ip address, etc.
rack-tor-block - A rack middleware to block accesses to your rails application from TOR nodes. Inspired by rack-block
ActionDispatch::RemoteIp from Rail's ActionController Middleware Stack - Checks for IP spoofing attacks.
Rack::Throttle - provides logic for rate-limiting incoming HTTP requests to Rack applications.
Alpaca - allows developers to quickly and easily configure and manage a whitelist and/or blacklist
Rack TCTP - middleware for enabling end-to-end security using the Trusted Cloud Transfer Protocol (TCTP)

Middlewares for WebSocket

faye-websocket-ruby - Standards-compliant WebSocket client and server. A general-purpose WebSocket implementation extracted from the Faye project
websocket-rack - Rack-based WebSocket server
SinatraWebsocket - Makes it easy to upgrade any request to a websocket connection in Sinatra

Middlewares for SEO

seojs-ruby - Rack middleware to integrate SEO.js to your Rails or Sinatra app. SEO.js makes your BackboneJS, AngularJS or EmberJS apps crawlable by Google to make them appear in search results
Rack SEO - Generate SEO friendly meta tags on the fly using Rack Middleware

Miscellaneous Middlewares

rack-pygmentize - use the generic syntax highlighter Pygments library to make your code look pretty!
rack-flash - Simple flash hash implementation for Rack apps.
sinatra-flash - An implementation of show-'em-once 'flash' messages for the Sinatra Web framework. (~ 50 LOC, note this is not a middleware.)
rack-emstream - Simple middleware for streaming with EventMachine-capable servers
sc - If static site generators were vegies, this one would be a pickle.
machined - A static site generator and Rack server built using Sprockets 2.0
rack-jekyll - Transform your Jekyll app into Rack application
Middleman - A static site generator using all the shortcuts and tools in modern web development. You can use Rack middlewares to modify content on-the-fly and intercept requests before they are processed by the server (Middleman). Middleman itslef has Rack middlewares to minify CSS and JavaScript files.
Brochure - Rack application for serving static sites with ERB templates (or any of the many template languages supported by Tilt)
Marley - A minimal blog engine without admin interface written in Sinatra framework. Use Rack::Auth::Basic to provide authentication.
rack-ssl - Rack middleware to force SSL
rack-ssl-enforcer - A simple Rack middleware to enforce ssl connections
rack-ssl-rails - A simple interface to Rack::SSL for Rails. Provides a railtie for use with rack-ssl
heroku-rack-ssl-enforcer-rails - Enforce SSL on Rails application on Heroku
Firehose - Firehose is both a Rack application and JavaScript library that makes building real-time web applications possible.
rack-capabilities - Discover just what rack can do (rather, what middleware you have installed)
rack-legacy - Run legacy environments like CGI and PHP under any rack server.
Rack::Recaptcha - Drop this Rack middleware in your web application to enable CAPTCHA verification via Recaptcha API.
Rack::Tunnel - Automatic port forwading via SSH tunneling
Rack::Mux - Multiplex multiple rack servers to the same app.
Rack::UserAgent::Filter - Rack Middleware for filtering by user agent
Rack::RevisionInfo - Rack middleware showing current git (or svn) revision number of deployed application
Rack::Health - A health check interface for rack applications.
Rack::Store - A Rack middleware what makes the env accessible anywhere while a request
Rack::Plastic - Helps you changing the HTML using Nokogiri
Rack::ToolBar - Allows you to create simple Rack Middleware that will insert HTML (or whatever!) into responses at specific points
Rack::Gsub - A Rack middleware wrapper for gsub
Rack::Codehighlighter - A middleware which allows for easy connecting a code highlighter of somebody's choice to an HTML page containing pieces of programming code.
Rack::JQuery - jQuery CDN script tags and fallback in one neat package.
Rack::JQueryUI - jQuery-UI CDN script tags and fallback in one neat package.
Rack::JQueryUI::Themes - jQuery-UI themes CDN script tags and fallback in one neat package.
Rack::Backbone - Backbone.js CDN script tags and fallback in one neat package.
Rack::Polymer - Polymer CDN script tags and fallback in one neat package. Polymer leverages web components, a new set of standards designed to provide reusable components for the web
Rack::Stream - A middleware for building multi-protocol streaming rack endpoints. It's also a simple Stream DSL.
Rack::StreamingProxy - A transparent streaming proxy to be used as rack middleware. Streaming proxy for Rack, the rainbows to Rack::Proxy's unicorn
Pusher - A Rack middleware that implement Ajax Push aka Comet
Robocop - a simple Rack middleware that inserts the X-Robots-Tag into the headers of all your responses
Rack::Geoip - A rack middleware component that handles simple geoip lookups.
Rack::GeoIPCountry - uses the geoip gem and the GeoIP database to lookup the country of a request by its IP address
Rack::CanonicalHost - https://github.com/tylerhunt/rack-canonical-host
committee - A collection of Rack middleware to support JSON Schema.
rack-async-stream - A asynchronous stream middleware based on EventMachine.

Helpers and Tools

From Rack built-in middlewares:
- Rack::Request - which also provides query string parsing and multipart handling.
- Rack::Response - for convenient generation of HTTP replies and cookie handling.
- Rack::MockRequest and Rack::MockResponse- for efficient and quick testing of Rack application without real HTTP round-trips.
- Rack::Builder - implements a small DSL to iteratively construct Rack applications.
- Rack::Lint - validates your application and the requests and responses according to the Rack spec.
- Rack::File - for serving static files.
- Rack::Directory - serves entries below the root given, according to the path info of the Rack request. If a directory is found, the file's contents will be presented in an html based index. If a file is found, the env will be passed to the specified app.
- Rack::Cascade - tries a request on several apps, and returns the first response that is not 404 or 405 (or in a list of configurable status codes).
- Rack::Utils - contains a grab-bag of useful methods for writing web applications adopted from all kinds of Ruby libraries.
- rackup - a useful tool for running Rack applications, which uses the Rack::Builder DSL to configure middleware and build up applications easily.
  
  rackup automatically figures out the environment it is run in, and runs your application as FastCGI, CGI, or WEBrick—all from the same configuration.
  - Rackup howto
rack-test - A layer on top of Rack's MockRequest similar to Merb's RequestHelper. (~ 200 LOC)
rack-test-test - an extension to rack-test that when combined with Test::Unit simplifies the process of unit testing properly designed RESTful API's
Lookout::Rack::Test - RSpec and Cucumber test helpers.
test-unit-capybara - integration testing helper library for Rack applications, a Capybara adapter for test-unit
rack_toolkit - A dynamic Rack server and helper methods to help testing Rack apps.
Split - Rack based ab testing framework designed to work with Rails, Sinatra or any other rack based app. Split is heavily inspired by the Abingo and Vanity rails ab testing plugins and Resque in its use of Redis
Rack::Scaffold - Automatically generate RESTful CRUD services
almost-rack - Rack in three lines of code.
rack-graph - Generate a tree displaying all your Rack middleware.
Apartment - Database multi-tenancy for Rack (and Rails) applications.

Miscellaneous

HTTP Clients

Faraday - Faraday is an HTTP client lib that provides a common interface over many adapters (such as Net::HTTP) and embraces the concept of Rack middleware when processing the request/response cycle.
rack-client - A HTTP client that aims to be a good Rack citizen.
rack-api - Create web app APIs that respond to one or more formats using an elegant DSL
weary - A framework and DSL for building RESTful web service clients. Full Rack integration
rest-core - Modular Ruby clients interface for REST APIs. rest-core consists of composable middleware that allows you to build a REST client for any REST API. Or in the case of common APIs such as Facebook, Github, and Twitter, you can simply use the dedicated clients provided by rest-more. See the slide The Promise of rest-core for more info.

Vagrant Middlewares

Videos: Rack Middleware as a General Purpose Abstraction by Mitchell Hashimoto
- the slide is available on speakdeck.
- Generalized middleware implementation for Ruby by Mitchell Hashimoto - ~ 130 LOC
Vagrant Middlewares - Vagrant calls middlewares "actions" and a stack of middlewares an "action sequence." (But you may also just call them middleware and middleware stacks, they’re mostly called the other names for histortical purposes)
- Vagrant::Action::Warden - The action warden is a middleware which injects itself between every other middleware, watching for exceptions which are raised and performing proper cleanup on every action by calling the recover method. The warden therefore allows middlewares to not worry about exceptional events, and by providing a simple callback, can clean up in any erroneous case
- Vagrant::Action::Builtin::BoxAdd - This middleware will download a remote box and add it to the given box collection.
- Vagrant::Action::Builtin::BoxCheckOutdated - This middleware checks if there are outdated boxes. By default, it only checks locally, but if box_outdated_refresh is set, it will refresh the metadata associated with a box.
- Vagrant::Action::Builtin::BoxRemove - This middleware will remove a box for a given provider.
- Vagrant::Action::Builtin::BoxUpdate - This middleware updates a specific box if there are updates available.
- Vagrant::Action::Builtin::Call - This middleware class allows a sort of "conditional" run within a single middlware sequence. It takes another middleware runnable, runs it with the same environment, then yields the resulting env to a block, allowing that block to determine the next course of action in the middleware sequence.
- Vagrant::Action::Builtin::ConfigValidate - This class validates the configuration and raises an exception if there are any validation errors.
- Vagrant::Action::Builtin::Confirm - This class asks the user to confirm some sort of question with a "Y/N" question. The only parameter is the text to ask the user. The result is placed in env[:result] so that it can be used with the Call class.
- Vagrant::Action::Builtin::DestroyConfirm - This class asks the user to confirm the destruction of a machine that Vagrant manages.
- Vagrant::Action::Builtin::EnvSet - This middleware class allows you to modify the environment hash in the middle of a middleware sequence. The new environmental data will take affect at this stage in the middleware and will persist through.
- Vagrant::Action::Builtin::GracefulHalt - This middleware class will attempt to perform a graceful shutdown of the machine using the guest implementation
- Vagrant::Action::Builtin::HandleBox - This built-in middleware handles the box setting by verifying the box is already installed, dowloading the box if it isn't, updating the box if it is requested, etc
- Vagrant::Action::Builtin::HandleBoxUrl
- Vagrant::Action::Builtin::HandleForwardedPortCollisions - This middleware class will detect and handle collisions with forwarded ports, whether that means raising an error or repairing them automatically.
- Vagrant::Action::Builtin::IsState - This middleware is meant to be used with Call and can check if a machine is in the given state ID.
- Vagrant::Action::Builtin::Lock - This class creates a multi-process lock using flock. The lock is active for the remainder of the middleware stack.
- Vagrant::Action::Builtin::Message - This middleware simply outputs a message to the UI.
- Vagrant::Action::Builtin::Provision - This class will run the configured provisioners against the machine.
- Vagrant::Action::Builtin::ProvisionerCleanup - This action will run the cleanup methods on provisioners and should be used as part of any Destroy action.
- Vagrant::Action::Builtin::SSHExec - This class will exec into a full fledged SSH console into the remote machine. This middleware assumes that the VM is running and ready for SSH, and uses the Machine#ssh_info method to retrieve SSH information necessary to connect.
- Vagrant::Action::Builtin::SSHRun - This class will run a single command on the remote machine and will mirror the output to the UI. The resulting exit status of the command will exist in the :ssh_run_exit_status key in the environment.
- Vagrant::Action::Builtin::SetHostname - This middleware sets the hostname of the guest according to the "vm.hostname" configuration parameter if it is set
- Vagrant::Action::Builtin::SyncedFolderCleanup - This middleware will run cleanup tasks for synced folders using the appropriate synced folder plugin
- Vagrant::Action::Builtin::SyncedFolders - This middleware will setup the synced folders for the machine using the appropriate synced folder plugin.
- Vagrant::Action::Builtin::WaitForCommunicator - This waits for the communicator to be ready for a set amount of time.

Vagrant Middleware Stack Builder and Runner

Vagrant::Action::Builder - Action builder which provides a nice DSL for building up a middleware sequence for Vagrant actions. This code is based heavily off of Rack::Builder and ActionDispatch::MiddlewareStack in Rack and Rails, respectively.
Vagrant::Action::Runner - This runner does the default expected behavior of running the middleware stacks in order, then reversing the order.
Vagrant::Action::Hook - This class manages hooks into existing Builder stacks, and lets you add and remove middleware classes. This is the primary method by which plugins can hook into built-in middleware stacks.

Inspiration

WSGI (Python) - The Web Server Gateway Interface (WSGI) is a specification for simple and universal interface between web servers and web applications or frameworks for the Python. WSGI is a Python standard described in detail in PEP 3333
Rack (Ruby) - Rack provides a modular and adaptable interface for developing web applications in Ruby. By wrapping HTTP requests and responses it unifies the API for web servers, web frameworks, and software in between (the so-called middleware) into a single method call.
Plug (Elixir) - Plug is A specification for composable modules between web applications, and it's also connection adapters for different web servers in the Erlang VM. Plug is sinatra-like, and Elixir has a Rails-like framework called Phoenix
Clack (Lisp) - Clack is a web application environment for Common Lisp inspired by Python's WSGI and Ruby's Rack.
Hack (Haskell) - Hack2 is a port of Ruby's Rack webserver interface.
JSGI (JavaScript) - JavaScript Gateway Interface, is an interface between web servers and JavaScript-based web applications and frameworks. It was inspired by the Rack for Ruby and WSGI for Python and was one of the inspirations of PSGI for Perl.
PSGI (Perl) - Perl Web Server Gateway Interface is an interface between Web servers and Perl-based Web applications and frameworks that allows writing portable applications that can be run as standalone servers or using CGI, FastCGI, mod_perl, et al. It is inspired by the Web Server Gateway Interface for Python, Rack for Ruby and JSGI for JavaScript.
WSAPI (Lua) - WSAPI is an API that abstracts the web server from Lua web applications. By coding against WSAPI your application can run on any of the supported servers and interfaces (currently CGI, FastCGI and Xavante, on Windows and UNIX-based systems). WSAPI's main influence is Ruby's Rack framework, but it was also influenced by Python's WSGI (PEP 333). It's not a direct clone of either of them, though, and tries to follow standard Lua idioms.
StackPHP (PHP) - a PHP interface for framework-agnostic code sharing
OWIN (.NET) - Open Web Interface for .NET, defines a standard interface between .NET web servers and web applications. The goal of the OWIN interface is to decouple server and application, encourage the development of simple modules for .NET web development, and, by being an open standard, stimulate the open source ecosystem of .NET web development tools. Katana is the implementation of OWIN components.

License

To the extent possible under law, coopermaa has waived all copyright and related or neighboring rights to this work.

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Contents

General

Tutorials

Presentations

Videos

Web Servers

Frameworks

Middlewares

Helpers and Tools

Miscellaneous

Inspiration

License