Overview

MassTransit is a free, open-source distributed application framework for .NET, designed to make building message-based, loosely coupled asynchronous systems straightforward. Rather than a standalone chat or server product, it is a developer library (installable via NuGet) that turns everyday .NET applications into reliable producers and consumers of messages — supporting everything from pub/sub to request/response to long-running sagas.

It provides the plumbing that lets microservices and background workers communicate without knowing about each other directly, which improves availability, reliability and scalability. Version 8 and earlier are Apache 2.0 licensed, and the framework integrates with popular brokers such as RabbitMQ, Azure Service Bus, Amazon SQS and ActiveMQ.

Key Features

• Transports: out-of-the-box support for RabbitMQ, Azure Service Bus, Amazon SQS and ActiveMQ, plus an in-memory transport for testing
• Sagas: model long-running, stateful business processes that react to a series of messages over time
• Pub/sub and request/response: publish events and send requests between services with retries and fault handling
• Riders and consumers: organise message consumers, scheduled messages, and stream-based riders for flexible routing
• Observability: hooks for logging, telemetry and integration with diagnostics so you can trace messages end to end
• .NET-native: first-class API for modern .NET, configurable via the familiar Microsoft DI container

Why Use It

MassTransit removes the boilerplate of wiring up a message broker, letting developers focus on business logic while the framework handles serialisation, routing, retries and sagas. Because v8 and earlier are Apache 2.0 licensed free software with an active open community, it is a solid foundation for event-driven and microservice architectures without vendor lock-in.

Use Cases

• Event-driven microservices that communicate asynchronously through a broker
• Order, payment and workflow pipelines modelled as stateful sagas
• Background job processing and service-to-service request/response in .NET applications

Platforms

.NET (a NuGet library supporting .NET 8/9, .NET Standard 2.0 and .NET Framework 4.7.2)

Licence

Apache License 2.0 (v8 and earlier, open source); v9 and later are source-available under a commercial licence

Website

masstransit.io