From L2 fundamentals to shipping on testnets: OP Stack mechanics, bridging, comparing Optimism/Arbitrum/Base, blob space, sequencer risks — then a practica

Course Information

Course Instructor

The W3D Team Author

Independent research on blockchain decentralization. Scores and methodology are maintained by the W3D Team.

1 · Core Lessons (CC-BY)

L2 Fundamentals: The OP Stack Model

Objective: understand what an L2 is, why the OP Stack design won, and what security you actually inherit from Ethereum.

Lab: Bridging to Base Safely

Objective: move assets between Ethereum and Base without becoming a bridge-hack statistic.

Optimism vs Arbitrum vs Base

Objective: choose between the three big optimistic L2s on evidence, not tribalism.

Blob Space and EIP-4844, Explained

Objective: understand the data layer that made cheap L2s possible — and its limits.

Sequencer Risks

Objective: evaluate the single operator standing between you and every major L2.

Deploy on Base Testnet

Objective: deploy a real contract to Base Sepolia with zero real money at risk.

Verifying Contracts on Explorers

Objective: prove a deployed contract matches its advertised code — the single most useful 5-minute check in DeFi.

Gas Optimization 101

Objective: stop overpaying for computation — as a user today, as a builder tomorrow.

Reading L2Beat Like an Auditor

Objective: turn L2Beat from a scary dashboard into a 3-minute risk verdict for any L2.

EigenLayer Restaking Lab

Objective: understand restaking by walking through it hands-on — without risking a wei of real stake.