API keys and JSON Web Tokens (JWT) are both used for authentication and authorization in API systems, but they differ in how they approach this. API keys authenticate and authorize using the same key, whereas JWT requires an initial authentication process to generate a token that contains user and application-level information, which is then used across the ecosystem to determine access rights. While API keys are simple and transparent, they can be cumbersome to manage and may leak if not properly secured. In contrast, JWT tokens are self-contained and provide more granular access control, making them suitable for large ecosystems with multiple services that need to communicate over a vast network. The use of JWT also enables centralizing authentication and authorization processes, which is crucial when each network or app requires different levels of access based on the user. Additionally, JWT provides a simple plug-and-play experience when adding new microservices or improving existing ones.