Postman supports multiple API protocols beyond HTTP and REST. Whether you’re working with a query language like GraphQL, a binary RPC framework like gRPC, or real-time protocols like WebSocket and MQTT, Postman provides a dedicated client interface for each one.
GraphQL is an open-source query language and runtime for APIs. Unlike REST, which exposes data through multiple endpoints, GraphQL uses a single endpoint and lets clients specify exactly the fields they need. This prevents over-fetching or under-fetching data. GraphQL is schema-driven, meaning clients can introspect the schema to understand available data fields before writing queries.
Postman’s GraphQL client loads automatically when you create a GraphQL request, providing a schema explorer and query builder. To learn more, see GraphQL in Postman.
gRPC is a schema-driven Remote Procedure Call (RPC) framework commonly used for inter-service communication in microservice architectures. It uses Protocol Buffers (protobuf) as its interface definition language to define services and message types, and transmits data over HTTP/2 for high performance and low latency. All four gRPC communication patterns are supported: unary, client streaming, server streaming, and bidirectional streaming.
Postman’s gRPC client lets you load a service definition, explore the available methods, and invoke them directly. To learn more, see Manage gRPC APIs using Postman.
MQTT (Message Queuing Telemetry Transport) is a lightweight publish/subscribe messaging protocol designed for devices and networks with limited bandwidth or power, such as IoT sensors and embedded systems. Clients connect to a central broker and exchange messages by publishing to topics or subscribing to receive messages from them.
Postman’s MQTT client lets you connect to a broker, subscribe to topics, and publish messages. To learn more, see MQTT in Postman.
SOAP (Simple Object Access Protocol) is a platform-independent, XML-based messaging protocol for exchanging structured information between services over HTTP. Although REST has largely replaced SOAP in modern API design, many enterprise and legacy systems still expose SOAP-based web services.
Postman can send SOAP requests over HTTP by adding the appropriate XML body and headers. To learn more, see Make HTTP calls using the SOAP protocol.
If you’re running a local server, Postman can send requests to it using Unix domain sockets (UDS) on macOS or Linux, or named pipes on Windows. These are forms of inter-process communication (IPC) that let processes on the same machine exchange data without a network connection, which is useful for testing local servers or containerized services.
To learn more, see Send requests over Unix sockets or named pipes.
Webhook listeners let you capture, inspect, and route incoming webhook events directly in Postman. Postman provides a public URL that you can register with any webhook provider, and every incoming event is logged with its headers, body, timestamp, and response status. You can replay events or route them to a target URL while you debug.
To learn more, see Webhooks in Postman.
The WebSocket protocol establishes a persistent, full-duplex connection between a client and a server over a single TCP socket. Unlike HTTP, either side can send messages at any time with low latency and minimal overhead. WebSocket is widely used for real-time applications such as chat, live data feeds, and multiplayer experiences.
Postman lets you create WebSocket requests, send and receive messages, and work with both standard WebSocket connections and Socket.IO connections. To learn more, see Send WebSocket requests with Postman.