API

Also called Application Programming Interface

An application programming interface: a defined way for one piece of software to talk to another, letting products connect, exchange data, and build on each other.

Why it matters

APIs let your product plug into the tools customers already use and let others build on you, which can become a growth channel and a moat. For many startups an open API is a strategic decision, not just a technical one.

For example

A payments startup exposes an API so any e-commerce site can add checkout with a few lines of code, turning integrations into a growth channel.

Related terms

SDK SaaS Platform

Go deeper

See how founders actually handle this on Building the product, part of the Starting Up hub.

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