Is a term used in categorizing protocols and methods in architectural models of computer networking. Both the OSI model and the Internet Protocol Suite (TCP/IP) define application layers.

In TCP/IP, the Application Layer contains all protocols and methods that fall into the realm of process-to-process communications via an Internet Protocol (IP) network using the Transport Layer protocols to establish underlying host-to-host connections.

In the OSI model, the definition of its Application Layer is narrower in scope, explicitly distinguishing additional functionality above the Transport Layer at two additional levels: Session Layer and Presentation Layer. OSI specifies strict modular separation of functionality at these layers and provides protocol implementations for each layer.

The common application layer services provide semantic conversion between associated application processes. Note: Examples of common application services of general interest include the virtual file, virtual terminal, and job transfer and manipulation protocols.

Application layer is the top layer of the OSI (Open System Interconnectivity) server layer model. This layer handles issues like network transparency, resource allocation and problem partitioning. The application layer is concerned with the user's view of network (e.g. formatting electronic mail messages). The presentation layer provides the application layer with a familiar local representation of data independent of the format used on the network.

The application layer provides the interface to the communications environment which is used by the application process. It is responsible for communicating application process parameters.

Application layer falls under the "host layers" in the OSI topologies used in network communication and it is also the top layer in the Internet model. The host layer also provide for accurate delivery of data between computers in the network.