What is an API key?

To access a program or application via an application programming interface, you need an API key. API keys are one-time keys consisting of a secret string of characters that authorizes access. With a key, the API can recognize authorized users and protect programs and systems from unauthorized access.

What’s the definition of an API key?

To connect and exchange functionalities between two programs, application programming interfaces, better known as APIs, are used. An API lets programmers, applications, apps, or projects interact with another service or program. In this way, an API can be used to control who’s allowed to make requests between APIs, who receives permission, and which data formats are used.

Access is controlled by one-time and unique authentication keys called API keys. API keys can be requested from API operators, among others. If users or applications have the appropriate key, the API server will grant you access.

How does an API key work?

API keys work similarly to passwords. As soon as an API “calls” another API and requests access, access permission is granted by exchanging the API key. The API key is assigned to the calling service or program and transmitted to the API server. If the API server confirms the authenticity of the API key, access to the program or certain functionalities is granted. In addition, API keys can be used to perform actions across applications via the API interfaces.

API operators define the access rights, data formats, and the scope of actions. In this way, it’s possible to determine exactly which type of users or projects receive access permissions and which actions are allowed via the programming interfaces. API keys can also be anchored directly in programming languages like JavaScript or Python. Users or services can request the key in JavaScript from the associated API server.

What are API keys used for?

API keys are mainly used in these areas:

  • Identification: An API key can identify “calling” APIs, projects, or services to the API server. This makes it possible to log who requested or received access, and who was denied.
  • Authentication: By exchanging the API key, it’s possible to check whether clients are actually authorized to access. It also checks whether the requested API is active.
  • Authorization: Once the project or service has been identified, the API server’s access rights determine the extent to which access is granted.

How can API keys be requested?

How you request or are assigned API keys depends on the API you want to connect to. Access rights vary based on the API operator. But usually the mapping of API keys follows this pattern:

  • Go to the website of the provider whose API you want to access and log in to the developer page.
  • Select API keys for existing projects or for creating new projects.
  • Rename the API key for clarity.
  • Once the API key has been created and assigned, you can insert it into the website or app for later access and data transfer. In future, the API server will recognize the calling application via the API key.

Want to know how to request an API key for apps like ChatGPT, Google Maps, or YouTube? Then take a look at these guides:

The advantages of API keys

The main benefit of API keys is the simple and fast authentication of access rights for users, services, or programs. Especially when connecting different applications to exchange data or perform cross-program actions. Authentication keys are also helpful to programmers creating an app who need access to a program via API. API servers can use the password-like keys to make sure no one gains unwanted access to the system.

API keys provide these enhanced authentication features:

  • Registration of APIs, programs, services, or projects that want to access specific APIs
  • Defined access rights of API servers and API operators to determine which APIs can authorize which kind of action and access
  • Overview of past allowed or denied access
  • Additional security as one-time, unique, and secret keys
  • Enabled blocking of unidentifiable network traffic
  • Control over the load by limiting the number of calls to an API
  • Additional filtering and assigning of certain access types or patterns to specific API keys

How important are API keys to security?

API keys alone are not a sufficient security measure, but provide an additional level of access security. Since API keys are owned by clients like passwords, there’s also a risk of them being stolen by hackers. Like a stolen password, unencrypted stolen API keys can quickly lead to unauthorized system access. Since API keys usually remain visible in server logs, they can give hackers access under the guise of supposedly legitimate access. Often, they’re involved in cyberattacks like DDoS attacks, man-in-the-middle attacks or injections.

What you should know about API keys and security:

  • API keys don’t identify specific users, but only APIs or programs that request access.
  • Unlike passwords, API keys are usually stored unencrypted on the client side and remain visible in server logs.
  • API keys, like unsafe passwords, can be stolen by hackers looking to gain access to an application.


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How can API keys be safely used?

Since programs use APIs to exchange sensitive data and grant access to internal applications, reliable API security is critical. Here’s how you strengthen APIs with additional security measures:

  • Restrict and protect access to client-side API keys.
  • Use a separate API key for each project and application.
  • Delete API keys that you no longer need.
  • Encrypt stored API keys as credentials-at-rest to prevent key theft.
  • Don’t integrate API keys into code in a clearly readable way or store in the source structure
  • Monitor the use of API keys, for example if several programmers are using REST APIs via OpenAPI.

API keys and data protection

Another important aspect of API keys is privacy. This starts when you install a new app on your phone and it asks for additional permissions. And you might not even be checking what permissions an app is requesting. If the service is questionable, you could unintentionally be giving away access to all your Facebook data, photos, or phone storage. The result is a comprehensive collection of data or, in an emergency, even a system takeover. To prevent data misuse, make sure to only give trusted apps access via an API key.

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