Definition
An API key is a string of characters that acts as a simple security credential for accessing an application programming interface (API). It identifies the calling application or user to the service that provides the API and is often used as a basic form of authentication. In many systems, especially in web and crypto-related services, the API key is included in each request so the server can decide whether to allow or deny access. While it helps control access, an API key alone is generally considered a lightweight security primitive and may be combined with stronger authentication methods.
In crypto and blockchain contexts, API keys are commonly used to connect wallets, trading bots, analytics tools, or other software to exchanges or blockchain data providers. The key links activity back to a specific account or project, enabling rate limits, permissions, and logging. Because it grants access to potentially sensitive actions or information, an API key is treated as a secret that must be kept confidential. If exposed, it can allow unauthorized parties to interact with the API as if they were the legitimate client.
In Simple Terms
An API key is like a secret ID code that an app shows to a service to prove who it is. When a program talks to an online service, it sends this key so the service knows which app is making the request. The service then uses the key to decide what that app is allowed to see or do. Because of this, an API key is closely related to authentication and must be protected from being shared or leaked.