Glossary
API
Meaning and details
An API is a defined conversation between programs. One side exposes endpoints, parameters and responses; the other calls them and reacts to what comes back. The web runs on HTTP APIs returning JSON, and the modern vocabu...
API meaning
An application programming interface: the contract through which one piece of software requests data or actions from another.
What is API?
An API is a defined conversation between programs. One side exposes endpoints, parameters and responses; the other calls them and reacts to what comes back. The web runs on HTTP APIs returning JSON, and the modern vocabulary around them, REST for resources, webhooks for push, GraphQL for client-shaped queries, OAuth for permission, rate limits for fairness, is the working literacy of anyone building software that touches anything else.
Why it matters to an indie builder: APIs are how small teams punch above their weight. Payments, email, search, maps, AI models, every heavy component of your product exists as someone else's maintained infrastructure behind an API key. Conversely, your own API, if you expose one, is a distribution channel: integrations built by customers and partners compound while you sleep, and marketplaces rank products by how well they connect.
A concrete example: a booking tool for tennis coaches. SMS reminders via a provider's API: four lines of code, no telecom compliance, no carrier relationships. Calendar sync through Google's API: read-only scope, free. The product's moat is the coach-specific workflow; the commodity capabilities around it are all rented through APIs for pennies per use. Two integrations, one afternoon, capabilities that would have taken a funded team a quarter to build in 2010.
Common mistakes: skipping the error paths (every API call can fail; handle 429 with backoff, retry idempotent calls, surface the rest honestly, see rate-limiting), hardcoding keys in the client, where anyone's browser devtools can read them (keys live server-side or in gateway functions), ignoring pagination and fetching everything per request, which works at 100 records and falls over at 50,000, and treating versioning as optional: providers deprecate, and unversioned integrations break on their schedule, not yours. The api trait blocks on IndieBoot mark the services that document these details well.