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title: Migration to Mule 4
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# Migration to Mule 4

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

For your Mule 3 apps to take advantage of Mule 4, migrate them to Mule 4 through one of the
following processes:

- A fully manual migration of connectors, modules, transports, expressions, and API gateways to
  their Mule 4 counterparts.

  For guidance with a fully manual migration, see [Prepare to Migrate](https://docs.mulesoft.com/mule-runtime/4.3/migration-prep) and review
  [Manual Migration Process](https://docs.mulesoft.com/mule-runtime/4.3/migration-process).

- A partially automated migration with the Mule Migration Assistant (MMA), which is available as an
  open source project on GitHub.

  For guidance using MMA to assist in a migration, see the
  [user documentation (on GitHub)](https://github.com/mulesoft/mule-migration-assistant/blob/master/docs/migration-intro.adoc#understand-the-mma-migration-process).
  MuleSoft suggests that you try MMA to determine whether you prefer it to a fully manual migration.
  Note that you can run MMA on a sample application by following steps in the
  [Migration Tutorial (on GitHub)](https://github.com/mulesoft/mule-migration-assistant/blob/master/docs/user-docs/migration-tutorial.adoc).

Important

**Mule Migration Assistant (MMA) is subject to the terms and conditions described for
[Community](https://www.salesforce.com/en-us/wp-content/uploads/sites/4/documents/legal/Agreements/versioning-back-support-policy.pdf)
connectors. Additionally, Mule Migration Assistant is distributed under the terms of the
[3-Clause BSD License](https://github.com/mulesoft/mule-migration-assistant/blob/master/LICENSE.txt).**

A benefit of using MMA is that it automates part of the migration of Mule 3 apps to Mule 4. Though
the MMA does not migrate the app entirely, it provides significant help with the following tasks:

- Migrating the project structure.

- Automatically creating descriptor files, such as `pom.xml` or `mule-artifact.json`.

- Automatically performing many adaptations of the app’s code.

- Providing guidance on how to manually migrate components and patterns that cannot be migrated
  automatically.

MMA helps with such tasks, but it does not deliver a fully functional app. Some additional steps are
required. Those steps include testing and can also include:

- Manual migration of unsupported components.

- Manual migration of complex MEL expressions to DataWeave that cannot be automatically converted by
  MMA.

- Manual migration of complex DataWeave transformations that cannot be automatically converted by
  MMA.

- Prior migration of the DataMapper with the DataWeave Migration tool, before running the MMA.

It is also important to note that the MMA does not support incremental migrations.