Client (computing)

Characteristics and components

Clients exist as both hardware and software. The software component—often called client software—implements communication protocols, user interfaces, and local storage. A familiar example is a web browser, which issues HTTP requests, renders responses, and manages cookies or cached content. Clients may keep minimal state or maintain complex session information depending on the application design.

Common examples

• Web browsers accessing websites (HTTP/HTTPS).
• Email clients that send and retrieve messages (SMTP, IMAP, POP).
• File transfer clients using FTP, SFTP or similar protocols.
• Remote access tools such as SSH clients and database client programs.

The client role is defined by initiating action: it asks for services and displays or processes the results for a user or another system.

History and distinctions

The client–server arrangement grew from early networked computing as tasks shifted from central mainframes to distributed machines. Over time distinctions arose: "thin" clients rely heavily on servers for processing and storage, while "thick" or "fat" clients perform more work locally. Client systems differ from peers in peer-to-peer models, where nodes both request and provide services.

Clients are central to modern computing: they shape how applications are designed, affect security and privacy considerations, and determine where updates and backups are managed. Because clients interact with remote servers, secure protocols, authentication, and update mechanisms are important aspects of their operation.