API key authentication is a security method that uses a unique string, called an API key, to identify and authenticate requests to an API. When you use API key authentication, you include this key in each request to prove that you have permission to access the API.

You use API key authentication to:

• Control who can access your API;
• Prevent unauthorized users from making requests;
• Track usage and monitor activity for each key.

API key authentication is simple to implement and works well for basic security needs. However, it is important to understand its limitations and best practices to keep your APIs safe.

How API Keys Work

An API key is a unique string that acts like a password for accessing an API. When you use an API key, you include it in your requests to prove your identity and get permission to use the API.

Passing API Keys in Requests

You usually send an API key in one of these ways:

• Add it as a query parameter in the URL, like https://api.example.com/data?api_key=YOUR_KEY_HERE;
• Include it in the request header, such as Authorization: Api-Key YOUR_KEY_HERE;
• Put it in the request body for APIs that accept data in the body (less common).

Most APIs prefer using headers, because it keeps the key hidden from browser history and logs.

Role of API Keys in Access Control

API keys help control who can use your API. When a request arrives, the API gateway checks if the key is valid. If it is, the request goes through. If not, the gateway blocks the request and returns an error. This process helps:

• Limit access to trusted users;
• Track usage by identifying which key made each request;
• Prevent abuse by blocking or limiting keys that make too many requests.

Example

Suppose you want to get weather data from an API. You receive an API key like 12345-abcde. You make a request:

GET https://weatherapi.com/current?city=Boston
Authorization: Api-Key 12345-abcde

The API gateway checks the key. If it's valid, you get the weather data. If not, you see an error message such as 401 Unauthorized.

By using API keys, you ensure only approved users and applications can access your API.