🐰 Learn Erlang
Open Source & In Active Development

Learn Erlang
Step-By-Step

We at Pennypack Software are starting a new project using Elixir. We prefer to build our understanding from the ground up, so we felt it was best to learn Erlang before learning its Ruby-inspired modern incarnation. We built this tutorial to teach ourselves Erlang and are open sourcing it to help others on the same journey.

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Open Source Tutorial in Active Development

This tutorial is open source and actively being developed. We're publishing lessons as we complete them to get community feedback and contributions. Subscribe to be notified when new lessons are added, or contribute on GitHub!

Hands-on Project

Build a real-time chat server handling thousands of concurrent connections

Interactive Koans

Master concepts through fill-in-the-blank exercises with instant feedback

Battle-tested Patterns

Learn OTP behaviors powering WhatsApp, Discord, and telecom systems

Why Erlang Powers the World's Most Reliable Systems

From WhatsApp handling billions of messages to Ericsson's 99.9999999% uptime telecom switches, Erlang's unique approach to concurrency and fault tolerance is unmatched.

True Concurrency at Scale

Spawn millions of lightweight processes, each with their own memory and garbage collection. No shared state, no locks, no race conditions.

"Let It Crash" Philosophy

Instead of defensive programming, embrace failure. Supervisors restart crashed processes in milliseconds, maintaining system integrity.

Hot Code Swapping

Update running systems without downtime. Deploy fixes while maintaining all connections and state.

erlang shell 
1> Pid = spawn(fun() -> 
       receive
         {hello, From} -> 
           From ! {ok, "Hello, World!"}
       end
    end).
<0.84.0>

2> Pid ! {hello, self()}.
{hello,<0.80.0>}

3> flush().
Shell got {ok,"Hello, World!"}
ok

A Structured Path to Mastery

35 lessons taking you from "Hello, World!" to building distributed systems. Each lesson builds on the last, with interactive exercises to cement your understanding.

01

Foundation

Lessons 1-8

Master Erlang syntax, pattern matching, and process fundamentals

02

Building

Lessons 9-20

Implement OTP patterns, TCP/WebSocket protocols, and chat features

03

Advanced

Lessons 21-35

Deploy distributed systems with monitoring, scaling, and operations

0

System Setup and Your First Project

Get your Erlang development environment set up and create the project structure for our WebSocket chat server

1

Your First Erlang Module

Learn Erlang's basic syntax, modules, functions, and data types by building utility functions for our chat server

2

Pattern Matching - Erlang's Superpower

Master Erlang's most powerful feature - pattern matching - to elegantly handle data structures and build robust chat server components

3

Recursion

Master recursive functions and learn how to break problems into smaller, manageable pieces using Erlang's powerful recursive programming model

4

Higher-Order Functions

Master higher-order operations like map, filter, and fold to build elegant data processing pipelines for our chat server

Plus 32 more lessons

Ready to Build Unbreakable Systems?

Start your journey into the world of fault-tolerant, distributed computing.

Begin Learning Erlang