If you've ever tried to build anything that talks to more than one crypto exchange - a portfolio tracker, an arbitrage bot, a price aggregator, a tax tool - you already know the dirty secret: every exchange's API is its own little universe . They all loosely speak REST and WebSocket, but the auth schemes, rate-limit models, error formats, symbol conventions, and pagination styles diverge in ways that turn "just fetch the ticker" into a multi-day yak-shave.

This guide is a developer-to-developer comparison of the five APIs you're most likely to integrate against - Binance, Kraken, Coinbase, Bybit, and OKX - focused on the things that actually matter when you're writing code: authentication, rate limits, how they want you to handle real-time data, and the specific footguns waiting in production.

I'll keep the marketing out of it.…