APIs are the contracts between software components. This guide covers every layer — from transport protocols up to security patterns, versioning, and real-world design decisions.
Core flow
Client ↔ API (contract) ↔ Server / data
Topics in this guide
API design quality spectrum
Free for students and teachers
Write notes like this one
Cards for every idea, quizzes and flashcards, read aloud — on the web and your phone.