API Fundamentals for Beginners
API fundamentals for beginners: what an API is, request and response anatomy, HTTP methods, status codes and pagination, each with a request you can run.
Track 1 of 9 in API 101, our free API testing course for beginners.
- For Manual testers
What is an API? A Plain-English Guide for Testers
An API is how two pieces of software talk to each other. Here's what that actually means — with runnable examples.
Request & Response Anatomy: Headers, Bodies, and Everything In Between
Every HTTP request has the same parts. Once you know them, every API you'll ever test becomes readable.
HTTP Methods Explained: GET, POST, PUT, PATCH, DELETE, QUERY
GET, POST, PUT, PATCH, DELETE — the five verbs that carry 99% of API traffic — plus QUERY, the emerging method for safe reads with a body. Here's what each one means, with runnable examples.
HTTP Status Codes: The Complete Tester's Reference
2xx means success, 4xx means you messed up, 5xx means they messed up — but the details matter. Here's the list every tester should know by heart.
Query Parameters, Pagination, Sorting & Filtering
Every useful API returns lists of things. Here's how to page through, sort, and filter them — with runnable examples.
Practice these lessons on your own APIs.
The Free Developer License of Shift-Left API is a single-user license that renews free every 6 months. Import your OpenAPI spec, generate tests, mock APIs and run workflows on your own machine. Want the full guides first? Browse the API testing hub.