ThickClients

A thick client, also called a fat client or rich client, is a client in a client–server architecture that performs substantial processing, data validation, and business logic on the client side. The application runs primarily on the user’s device, while the server provides data services and centralized storage. Thick clients can operate offline or with intermittent connectivity, though they may still synchronize with a server when available.

Characteristics include local processing power, a relatively rich user interface, and the ability to function with limited server interaction. They typically require platform-specific installation, consume more local resources, and manage data storage and updates on the client. Security and data synchronization are more complex due to data that may reside on the client.

Compared with thin clients, thick clients offload processing from the server to the client, reducing server load and latency for certain tasks but increasing client maintenance, deployment complexity, and the risk of data divergence during offline periods.

Common examples and use cases include traditional desktop applications (word processors, CAD, image editors), enterprise front-ends such as SAP GUI or Oracle Forms, database management tools, and other software that benefits from an offline-capable, feature-rich UI.

Advantages of thick clients are responsiveness, richer user experience, and offline operation. Disadvantages include higher maintenance costs, more complex updates, platform fragmentation, and greater security considerations due to data stored on client devices.

In modern architectures, many applications aim to minimize thick-client use through web technologies or hybrid delivery, while some domains retain thick clients for performance, offline access, or regulatory needs.