What is a Bitcoin Exchange?
A Bitcoin exchange is a marketplace where you buy, sell, and trade bitcoin. The two main types are centralized exchanges (CEX) and decentralized exchanges (DEX). Centralized exchanges like Coinbase, Kraken, and Binance hold your funds in custody and match your trades against other users on the platform. Decentralized exchanges let you trade directly from your own wallet using smart contracts, with no third party holding the funds.
Why It Matters
Exchanges are how most people buy their first bitcoin. They convert dollars (or any other fiat currency) into BTC and back. They aggregate supply and demand from millions of users, which is how the global price gets discovered.
They are also the biggest risk in the Bitcoin ecosystem. Mt. Gox collapsed in 2014 after losing 850,000 BTC. Bitfinex was hacked in 2016 for 120,000 BTC. FTX imploded in November 2022 and took $8 billion in customer funds with it. Celsius and Voyager froze withdrawals before bankruptcy the same year. The pattern is consistent enough that long-term holders have a phrase for it: "not your keys, not your coins."
The lesson isn't to avoid exchanges. They're necessary infrastructure. The lesson is to treat exchange custody as temporary. Buy on the exchange. Move what you intend to hold long-term to self-custody.
How It Works
Centralized exchanges operate like traditional brokerages. You create an account, verify your identity through KYC, link a bank account, and deposit funds. The exchange holds your fiat in bank accounts and your bitcoin in custody. When you place an order, the exchange matches you with a counterparty and updates internal balance records.
The trades you make on a centralized exchange aren't on-chain transactions. They're database entries. Your bitcoin only moves on the actual blockchain when you withdraw it to an external address. Your own wallet, ideally.
Decentralized exchanges work differently. You connect a wallet you control to a smart contract that handles the swap. No identity verification, no fund custody, no waiting on the exchange to process anything. DEXs offer more privacy and full self-custody but typically have less liquidity and a steeper learning curve than centralized exchanges.