Buildathons.ai

Bitcoin & Blockchain Fundamentals Course

Understand how Bitcoin works under the hood — cryptographic hashing, UTXO model, transaction signing, and building a mini-blockchain in JavaScript. Follow…

Course overview

Understand how Bitcoin works under the hood — cryptographic hashing, UTXO model, transaction signing, and building a mini-blockchain in JavaScript.

How Bitcoin Actually Works

Bitcoin is a decentralized ledger of transactions — no bank, no central server. Key concepts: Blockchain: A chain of blocks, each containing transactions. Each block references the previous via its hash. Mining: Proof-of-Work — miners race to find a nonce that makes SHA-256(block data) start with N zeros. UTXO Model: Unlike bank balances, Bitcoin tracks unspent transaction outputs (UTXOs). Spending = consuming UTXOs and creating new ones. Transaction Signing: Every spend requires a cryptographic signature from the private key owning the UTXO.

Build a Mini-Blockchain in JavaScript

Let's implement the core data structures of a blockchain — blocks with SHA-256 hashing and a proof-of-work system.

Working with the Bitcoin RPC & mempool.space API

For real Bitcoin data without running a full node, use the mempool.space REST API — no API key required.