A client is a computer or software that accesses a server and retrieves special services or data from it. It is the task of the client to standardize requests, transmit them to the server, and process the data obtained so that it can be displayed on an output device such as a screen. A client does not execute server tasks, but is merely an intermediate element. Typical clients are web browsers or email clients.
Since the 1960s, clients serve the purpose of enabling communication between hardware and servers. One of the oldest protocols is the Telnet protocol. Even today clients work in a similar fashion. The client sends a request to a server or multiple servers and receives data that it interprets and outputs it in a readable form to a user. The client must use a specific protocol to communicate with the server.
In order for the data to be available for other applications, two different data caching options exist, either on the server or client side. A widely used option to store user data on the client are cookies.
The following clients are currently frequently used:
Rich clients use the server as little as possible and perform most of their duties locally. These clients are usually completely modular systems such as development environments. In contrast, thin clients work with as little hardware as possible and try to perform all tasks on the server side.
When programming websites, their presentation should be tested with different clients, i.e. web browsers, because in many cases there are differences depending on the CMS that affect the usability and consequently often also the number of conversions. The adjustment of websites to the respective clients and testing the display of content on different browsers belongs therefore within the scope of SEO.