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# Introduction to Mule 4 for Mule 3 Users

> For the full documentation index, see: https://docs.mulesoft.com/llms.txt

If you are a user that already knows Mule 3 and recently migrated to Mule 4, review the following
introduction to learn the main changes in Mule 4.

If you are an experienced Mule 4 user, go directly to our [Mule Runtime](https://docs.mulesoft.com/mule-runtime/4.3/) documentation instead.

Mule 4 simplifies the expression language and reduces management complexity so that you can speed up
the on-ramping process and deliver applications faster than in Mule 3.

Conceptually, you can think of Mule 4 as an evolution of Mule 3. Many of the core concepts are the
same: applications, flows, connectors, DataWeave, and so on. However, because it is simpler, there
is less to learn and less for you to manage.

This overview takes you through the high-level changes in Mule 4 so that you can quickly learn the
basics. It covers these topics:

- [Mule Message](https://docs.mulesoft.com/mule-runtime/4.3/intro-mule-message)  
  The Mule Message structure has evolved to make it easier to work with properties and to provide
  more consistency across connectors.

- [Expression language](https://docs.mulesoft.com/mule-runtime/4.3/intro-expressions)  
  The Mule Expression Language has been replaced with the DataWeave language so that you work with
  data and learn Mule more easily.

- [Connectors](https://docs.mulesoft.com/mule-runtime/4.3/intro-connectors)  
  The approach to connectivity was unified in Mule 4. Mule 3 transports were replaced with new
  operation-oriented connectors that are easier to use, have better out-of-the-box defaults, and
  provide new advanced capabilities.

- [Error Handling](https://docs.mulesoft.com/mule-runtime/4.3/intro-error-handlers)  
  Easier and more powerful error handling with a new Try scope.

- [DataWeave](https://docs.mulesoft.com/mule-runtime/4.3/intro-dataweave2)  
  DataWeave includes minor changes to simplify the syntax and make it easier to learn.

- [Studio 7](https://docs.mulesoft.com/mule-runtime/4.3/intro-studio)  
  Features a simplified palette, improved Maven integration, and many other usability improvements.

- [Runtime engine](https://docs.mulesoft.com/mule-runtime/4.3/intro-engine)  
  The internal execution engine has been updated with a new self-tuning and non-blocking reactive
  engine. This allows for better performance and scalability out-of-the-box.