Rack Middleware to proxy requests to a remote server. This is usefull for proxying AJAX request to remote services, thanks to @cwninja.

A healthcheck interface for Sinatra and Rails framework

Rack middleware for idempotency guarantees in mutating endpoints.

Rack jwt auth middleware

Rack middleware for handling large file uploads. Integrates nicely with the Nginx upload module: http://www.grid.net.ru/nginx/upload.en.html

Rack::LTI provides LTI launch and configuration endpoints to your Rack-based application. It handles configuration, authorization, and routing. For more information about LTI, see http://www.imsglobal.org/toolsinteroperability2.cfm.

A rack middleware to output access log in ltsv format

Provides a simple router & dispatcher for Rack.

Rack parameter validation and type coercion.

Small rack middleware to block your site from unwanted vistors. A little bit more convenient than basic auth - browser will ask you once for the password and then set a cookie to remember you - unlike the http basic auth it wont prompt you all the time.

Includes {'X-Clacks-Overhead': 'GNU Terry Pratchett'} header inside any rack application. http://redd.it/2yt9j6

Private Rack middleware purpose is to protect your Rack application from anonymous via a secret code form.

A simple profiler for Rack applications, only depending on ActiveSupport::Notifications

Handle race conditions in Rails JS feature tests caused by outstanding overlapping actions in your app, with rack middleware to let you wait for pending feature test actions to finish

Show server status

Slightly smarter session cookies for Rack 2 apps

Rack middleware that deletes cookies at designated paths, including support for wildcard patterns for flexible cookie management.

Analyze timing and process info from your Rack stack.

A web console for Rack apps.

A Rack profiler for web applications.