What is an API?

An API, short for application programming interface, is a defined way for one piece of software to talk to another. An API spells out which data and actions are available, and exactly how other systems can use them.

In practice, an API is a set of rules, or contracts, that describe how to send a request and what kind of response to expect. For example, a webshop can use a payment provider's API to create a transaction, check its status, and receive confirmation without ever seeing the provider's internal code. The API sits in between, so teams can connect tools fast, keep systems loosely coupled, and still work in a predictable way.

How an API works in simple terms

Most modern APIs use HTTP as the transport layer and exchange data in formats like JSON. A client, such as your ecommerce platform or marketing automation tool, sends a request to an API endpoint like /orders or /customers. The API checks the request, applies business rules, talks to databases or other services, then returns a structured response.

From a marketing and growth perspective, an API is what makes your stack plug and play. You can push events from your webshop into analytics, sync leads from your website into a CRM, or trigger campaigns in your automation platform, all by using well documented APIs instead of manual exports.

Key types of API you will encounter

For digital and ecommerce teams, the most common flavour is a web API, often called a REST API. It exposes resources via URLs and uses standard HTTP methods like GET, POST, PUT and DELETE. You will also see third party SaaS platforms provide partner APIs for deeper integrations, and internal APIs that your own developers use to keep backend systems modular and maintainable.

Each API defines authentication rules, such as API keys or OAuth tokens, to control which applications can access which data. Well designed APIs also include rate limits and versioning so your team can build reliable automation without breaking changes every month.

Why APIs matter for growth teams

  • APIs connect your tools into a coherent growth stack, from webshop and CRM to analytics and ad platforms.
  • They let you automate repetitive work, which is the basis for scalable workflows and advanced marketing automation.
  • APIs enable programmatic data flows, which you need for tactics like programmatic SEO or dynamic ad feeds.
  • They reduce vendor lock in, since you can swap or add tools as long as they expose a solid API.
  • For technical SEO and analytics, APIs power custom dashboards and tools such as the 6th Man SEO extension.

Used well, an API turns your website, webshop and marketing platforms into a flexible system that can evolve with your goals. Instead of being limited by what a single tool offers out of the box, your team can orchestrate data and actions across services, supported by focused utilities from the 6th Man tools library when needed.