[[introduction]]
== Introduction

Cowboy is a small, fast and modular HTTP server written in Erlang.

Cowboy aims to provide a complete xref:modern_web[modern Web stack].
This includes HTTP/1.1, HTTP/2, Websocket, Server-Sent Events and
Webmachine-based REST.

Cowboy comes with functions for introspection and tracing, enabling
developers to know precisely what is happening at any time. Its modular
design also easily enable developers to add instrumentation.

Cowboy is a high quality project. It has a small code base, is very
efficient (both in latency and memory use) and can easily be embedded
in another application.

Cowboy is clean Erlang code. It includes hundreds of tests and its code
is fully compliant with the Dialyzer. It is also well documented and
features a Function Reference, a User Guide and numerous Tutorials.

=== Prerequisites

Beginner Erlang knowledge is recommended for reading this guide.

Knowledge of the HTTP protocol is recommended but not required, as it
will be detailed throughout the guide.

=== Supported platforms

Cowboy is tested and supported on Linux, FreeBSD, Windows and OSX.

Cowboy has been reported to work on other platforms, but we make no
guarantee that the experience will be safe and smooth. You are advised
to perform the necessary testing and security audits prior to deploying
on other platforms.

Cowboy is developed for Erlang/OTP 18.0 and newer.

=== Versioning

Cowboy uses http://semver.org/[Semantic Versioning 2.0.0].

=== Conventions

In the HTTP protocol, the method name is case sensitive. All standard
method names are uppercase.

Header names are case insensitive. Cowboy converts all the request
header names to lowercase, and expects your application to provide
lowercase header names in the response.

The same applies to any other case insensitive value.