Stage 2: Lightning Network

Build scalable Bitcoin payment solutions with Layer 2

~3.5 hours 4 modules Lightning Developer badge

Welcome to Lightning Network Development

Bitcoin's base layer settles ~7 transactions per second. Lightning Network is a Layer 2 solution that enables millions of instant, low-cost payments per second while maintaining Bitcoin's security guarantees.

In this stage, you'll learn how Lightning works at a protocol level, understand the cryptographic primitives that enable trustless off-chain payments, and build your first Lightning application.

Modules

Module 1: Payment Channels

1
Understand the foundation of Lightning: bidirectional payment channels. Learn how two parties can transact thousands of times with only two on-chain transactions (open and close).

Topics Covered:

  • Channel construction and funding
  • Commitment transactions
  • Revocation mechanism (penalty transactions)
  • Channel states and balance updates
  • Interactive Lightning Lab demo

Module 2: Routing & HTLCs

2
Master Hash Time-Locked Contracts (HTLCs) and understand how Lightning routes payments across a network of channels without trusted intermediaries.

Topics Covered:

  • Hash Time-Locked Contracts (HTLCs)
  • Multi-hop payment routing
  • Onion routing for privacy
  • Path finding algorithms
  • Interactive route simulator

Module 3: Lightning Application Development

3
Learn to build Lightning applications using LND, c-lightning, or Eclair. Create invoices, handle payments, and build a simple Lightning-powered app.

Topics Covered:

  • Lightning implementations (LND, CLN, Eclair)
  • REST and gRPC APIs
  • WebSocket subscriptions for real-time updates
  • BOLT 11 invoice format
  • Code: Build a Lightning invoice generator

Module 4: Beyond Lightning - The Future of Bitcoin Layers

4
Explore Bitcoin's evolving layer ecosystem beyond Lightning: Liquid, Fedimint, Drivechains, and emerging protocols. Understand the tradeoffs and how each layer extends Bitcoin's capabilities.

Topics Covered:

  • Bitcoin's layered architecture philosophy
  • Liquid Network (privacy & institutional layer)
  • Fedimint (community custody & eCash)
  • Drivechains & experimental sidechains
  • Interactive layers explorer map

Congratulations! Stage 2 Complete!

You've earned the "Lightning Developer" badge! You now understand payment channels, routing with HTLCs, and can build Lightning applications.

Continue to Stage 3: Building Applications →