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MassTransit is the .NET messaging framework that keeps modern systems moving reliably, securely, and at scale.

From simple message consumers to saga state machines and routing slips, it gives teams powerful capabilities through a consistent programming model while reducing integration complexity and operational overhead.

With over 200 million downloads and more than 200,000 deployments worldwide, MassTransit is trusted by organizations of every size in over 150 countries.

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Features

Core Concept

Consumers and Endpoints

Build message-driven services with strongly typed consumers and automatic endpoint configuration. MassTransit resolves consumers through DI, manages message locks, and acknowledges only when processing succeeds.
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Core Feature

Automatic Broker Topology

Use message contracts and consumer definitions to create and validate queues, exchanges, topics, and subscriptions automatically. MassTransit keeps transport topology aligned with your code and conventions.
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Reliability

Retry, Redelivery, and Faults

Recover gracefully from transient and prolonged failures with retry and delayed redelivery policies. When processing fails, fault events and error queues provide clear paths for diagnosis and recovery.
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Reliability

Outbox Consistency

Prevent duplicate or premature publishes by buffering outbound messages until consumer or saga persistence succeeds. Choose in-memory outbox for speed or transactional outbox for durable delivery.
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Business Logic

Saga State Machines

Orchestrate long-running workflows with state, events, and correlation rules using an expressive C# state machine syntax. Persist saga state across messages to orchestrate complex distributed transactions.
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Business Logic

Routing Slips

Execute dynamic multi-step workflows with built-in compensation for distributed transactions. Routing slips support per-request itineraries and integrate naturally with sagas for visibility and recovery.
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Application Pattern

Request Client

Use asynchronous request/response when a service needs an immediate answer without blocking threads. MassTransit request clients handle responses, faults, and cancellation through a task-based API.
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Deployment

Transport Flexibility

Run the same messaging code across RabbitMQ, Azure Service Bus, Amazon SQS/SNS, SQL transport, and more. MassTransit provides a consistent programming model while exposing transport-specific capabilities when needed.
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Testimonials

MassTransit gave us enterprise-grade messaging without the maintenance burden of a home-grown system. Our engineering velocity increased immediately.

CTO, National Retailer

MassTransit has the best developer ergonomics of any service-bus library we tested. Our team was productive on day one.

Engineering Director, Government Contractor

We compared build-vs-buy. The cost of maintaining our own messaging layer was multiples higher than licensing MassTransit.

CTO, Healthcare SaaS Provider

The built-in sagas and routing slips let us implement complex workflows without reinventing anything.

Sr Engineer, Global Distribution

License Pricing

Single Line

Perfect for small organizations with single product line
  • One product, including all services and deployments
  • Flat-rate pricing, no per-message or per-endpoint fees
  • Annual subscription with perpetual downgrade rights
  • Email support with a 72-hour response time

Multiple Line

Suitable for multiple product lines within an organization
  • Everything in Single Line
  • Multiple products, services, and deployments
  • Guidance for cross-team deployments and scaling
  • Email support with a 48-hour support response time
All payments are processed securely through Stripe and support major credit cards and bank transfers. Amounts shown are in US Dollars.
After direct payment, your license key is delivered within minutes to the email address you provide. If you prefer to pay by invoice, Contact Us directly.

Frequently Asked Questions

Do I need a license for development or test environments?
Your license covers all environments, including environments used for development, testing, staging, and production, within the scope of the license.
Are there limits on developers, services, endpoints, or messages?
Your license includes all developers and services in all environments. You are not charged any additional per-endpoint or per-message fees.
What constitutes a product line in this context?
A product line refers to a single, cohesive software system or family of services that together make up one functional product. For example, an application, platform, or backend supporting a specific business domain is considered a single product line. The license covers all related services, components, APIs, and background processes across all environments (development, testing, staging, and production). Each product line typically has its own release cycle, infrastructure, or codebase. Organizations that operate multiple independent systems or business units can use an organization-wide (multi-line) license, which covers all product lines under one agreement.
What happens if my license expires?
If your license expires, you retain perpetual rights to continue using any MassTransit version released during your active subscription period. A current, active license is required when upgrading to newer versions or requesting support. This ensures that an application built and deployed using MassTransit with a valid license will continue to run even after the license has expired.
Will MassTransit v9 be open source?
MassTransit v9 will not be open source under a permissive license like previous versions, but it will remain source-available. The full source code will continue to be hosted on GitHub, accessible to licensed customers and community users with appropriate permissions. This ensures transparency, auditability, and the ability to review or debug the framework while maintaining a commercial licensing model. The codebase, APIs, and development process will remain open for review, but redistribution or modification outside the license terms will require authorization.
What about licensing for agencies or consultancies?
Agencies and consultancies are licensed based on how they engage with their clients. A commercial license is required for any projects that use MassTransit while under the agency’s development or maintenance. If ownership or ongoing maintenance of the application is later transferred to a client, that client must obtain their own MassTransit license to continue updating the software. Agencies can use one multiple line license for all projects they actively maintain, provided those applications remain under their management. This ensures that both development partners and clients are properly licensed for their respective roles.
Is there a free or discounted license available?
Organizations with gross annual revenue under one million (USD) may qualify for a 100% discount on a MassTransit license. This includes full access to all features and functionality of the licensed version, but does not include commercial support (community support remains available through public discussion channels and the official documentation). This program is designed to make it easy for startups, independent developers, and smaller teams to adopt MassTransit early, build confidently, and transition to a commercial support plan as they scale. Once your organization’s annual revenue exceeds one million (USD), you’ll need to pay for a commercial license at your next renewal.
Will there be a free license for non-profits?
Non-profit organizations with annual expenses under one million (USD) may qualify for a 100% discount on a MassTransit license.

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Get more information on MassTransit, and find out how you can license MassTransit for use in your organization.