What Is an API Key? How To Use API Keys

What do YouTube, Google Maps, X, Spotify, and OpenWeatherMap have in common? You can embed their content outside their native habitats. This is possible thanks to application programming interfaces (APIs).

APIs are, effectively, the means of communication between two types of software—your website, for instance, and that Spotify playlist you want to embed. They provide wide public access to digital tools. However, much like a building with restricted access, you must limit to whom you grant permission to avoid misuse. That’s where API keys come in.

What is an API key?

An API key is a unique identifier that can authenticate requests you make to an application programming interface (API). API technology lets versions of a software product appear on third-party websites.

If you’ve ever pressed play on a Spotify playlist on a blog or interacted with a Google Maps widget on a hotel’s website, you’ve used an API. And the website you visited used an API key to access that API and its data.

API keys can secure the interface by ensuring only specific users or authorized applications can access and interact with the API. A specific API key, or private API, controls access to services or data—essentially a form of user authentication to validate that a person or entity has permission to access that information.

Public vs. private API keys

API keys can identify projects, grant project authorization, and manage application usage. They also allow API providers to set limits on who can access this information and how many times, which can prevent abuse, like spamming or a data breach. Two main types of keys control API calls: public keys and private keys. Here’s how they compare in security and confidentiality:

Security

Public application usage rarely requires the exchange of top-secret data, so public API keys don’t offer the strongest levels of protection.

Private API keys are more secure, and you can typically use them for accessing sensitive data or performing critical operations within an API. Often they are a part of proprietary applications or in-house record-keeping tools that require API keys for security purposes. Private API keys might also require a secret token or other security mechanisms to enhance application usage tracking and prevent unauthorized access. They also allow filter logs (looking at subsets of data depending on different criteria) to track the behavior of authorized applications and detect any potential misuse.

Confidentiality

Anyone can access public API keys. You might see randomly generated characters in the request header or URL query string during an API call. If you look carefully at a long URL for an embedded YouTube video, you may notice unique API keys at the end.

You must not share private API keys—which the application securely stores—with anyone.

How API keys work

API keys play an essential role in ensuring the security of your application programming interface. They offer access control so only approved users and apps can access the sensitive data within an API. Here’s a summary of how API keys identify users and grant access:

Generation

An API provider generates a string of characters for each user or app that needs to access the API. This unique API key acts as a credential, proving the request comes from an authorized source.

Authentication

When a user makes an API request, it includes the API key. The API server verifies the API key against a database of authorized keys. If the key is valid, the server grants API access. For invalid or missing keys, the API provider denies access.

Application access

With approved API requests, the API server will authorize access to its resources. The level of access and API usage depends on the key’s permissions. For instance, if the API key identifies the requester as a developer account, the server may grant full access. If the key identifies third-party application traffic, this may prompt far more limited access to the API’s services.

Rate limiting

To prevent abuse and ensure fair usage, API providers often implement rate limiting, or a cap on how many times an application can make requests within a specified period, keeping API consumption at reasonable levels. Rate limiting ensures that many different people and applications have access to the API.

Security

While API keys serve as a basic form of authentication, you can also combine them with other security mechanisms—like IP whitelisting, encryption, or OAuth tokens—to identify application traffic and enhance security. In all cases, you should treat API keys as sensitive information and keep them confidential. You should never share them publicly or hard code them into applications.

Common uses for API keys

System administrators use API keys to control access to APIs, ensure security, and facilitate API integrations. These keys offer a critical line of security against data thieves and third-party applications that might otherwise overtax an API. Here are some of the most common ways in which API keys are used:

Controlling access

API keys control access to an API’s data or services, ensuring only authorized applications can make API calls. When an API producer provides a key to a requesting application, they’re allowing that app to interact with their services, such as to retrieve data or perform specific actions.

Private API keys are especially important for securing sensitive data, while public API keys are suitable for less sensitive operations. Project API keys on platforms like Google Cloud Platform Console allow developers to control access based on specific projects.

User authorization

API keys may also pair with authentication tokens for secure authorization. This ensures that only authenticated and authorized users can interact with the API. Key usage (whether or not it requires a secure authentication token) will block anonymous traffic and protect against potentially malicious activity.

Identifying usage patterns

API keys help API providers identify usage patterns by tracking which individual users or applications are behind an API call. This tracking allows providers to monitor application usage, set rate limits, and optimize the overall service. For example, YouTube API keys identify how frequently specific applications access videos or data, and Google Maps API keys can track location data requests.

Blocking unauthorized traffic

API keys can block anonymous traffic by only processing requests with a valid API key. Private API keys ensure only legitimate traffic can gain access while blocking requests to prevent potentially malicious activity.

Automating integrations and application tasks

You can use API keys to automate tasks for software or systems that need to integrate with third-party services. For example, developers implement API keys to automate data retrieval from external sources, like using YouTube API keys to pull video data into an application. API key management helps to keep these integrations secure and reliable.

Best practices for using API keys

The secure and efficient use of API keys will prevent unauthorized access from malicious users, and it will let you maintain control over API calls and project authorization. Here are a few best practices to implement when using API keys:

1. Store your API keys securely. Never store API keys in plain text within your application; instead use secure methods like environment variables or encrypted configuration files to protect them.

2. Limit access when possible. Grant API keys only the necessary permissions to perform their intended functions as granting broad access can lead to unintended consequences.

3. Regularly rotate your API keys. Just as internet users should rotate their passwords, system administrators should periodically regenerate API keys to reduce the risk of unauthorized access.

4. Monitor key usage. Keep track of API key usage patterns to detect potential security breaches or unauthorized access.

5. Implement rate limiting. Limit the number of requests a user can make using an API key within a specific period to prevent abuse and ensure fair usage so your software won’t crash in a flood of requests.

6. Use API key management tools. Consider using specialized API key management tools to simplify the process of generating, storing, changing, and revoking keys.