API
An API, or Application Programming Interface, is a defined interface that allows software to interact with another piece of software.
Instead of a person clicking through a user interface, another program follows the API's documented rules.
MDN's API glossary describes an API as an interface that enables software to interact with another application, service, or system.
What It Means in Practice
Imagine a booking platform contains:
- Reservations
- Guests
- Availability
- Rates
A website does not necessarily need direct access to the platform's database.
The platform might instead provide an API that lets authorized software request information such as:
Give me available rooms for July 12–14.
or:
Create this reservation.
The API creates a controlled interface between the systems.
What an API Can Allow
Depending on the service, an API may allow software to:
- Retrieve information
- Create records
- Update records
- Delete records
- Trigger actions
- Upload files
- Search data
- Start workflows
- Check system state
The available actions are normally divided into API Endpoints.
API vs. User Interface
A user interface is designed for people.
An API is designed for software.
For example:
Human → opens the CRM → clicks New Contact → fills in a form
API → sends a structured request → CRM creates the contact
Both may ultimately perform the same business action.
Why It Matters
APIs make automation and system integration possible without relying on fragile techniques such as copying information from visible web pages.
They can support:
- CMS Integration
- Inventory Sync
- Headless CMS
- Content APIs
- Payment systems
- Booking systems
- Analytics
- Automation
Common Problems
Common API problems include:
- Poor documentation
- Missing authentication
- Rate limits
- Breaking changes
- Inconsistent data
- Integrations depending on undocumented behaviour
- Credentials embedded in public code
- Errors being ignored
- Systems assuming every request succeeds
How to Improve
Treat the API as a contract.
Understand:
- What operations exist
- Which data each operation expects
- How Authentication works
- What Authorization is granted
- Which Rate Limits apply
- How errors are returned
- Which API Version is being used
Build the integration around documented behaviour rather than assumptions.