Thick clients, also known as heavy clients, are network-connected devices with many features. Thick clients are useful whether they are linked to a network or not, in contrast to thin clients, which lack hard disks and other features.

A thick client is completely usable even when not linked to the internet, but it is only a "client" when it is. Programs and data that are not kept on the local machine's hard drive might be made available to the fat client by the server. Thick customers are frequently offered to workers by companies. They can use the laptops without Internet connectivity or view data on a local server thanks to this. A heavy client is frequently referred to as a desktop when it is not linked to the network.