If you are migrating an existing install to Altis check out the migrating guide first.

When new versions of Altis are released you will need to manually upgrade your project to the new version. New versions can bring anything from breaking changes to new features. It's important you read the changelog / upgrade notes for the specific version you are upgrading to. When upgrading multiple versions at once, be sure to follow the release notes on all intermediate versions.

To switch the version of Altis for your project, modify the version constraint for the altis/altis dependency in your composer.json. For example, to upgrade to Altis version 17.

	"name": "company-name/my-site",
	"require": {
		"altis/altis": "^17.0.0"
	"require-dev": {
		"altis/local-chassis": "^17.0.0",
		"altis/local-server": "^17.0.0"

Next run rm -rf vendor on MacOS or Linux, or on Windows rmdir vendor.

Note: this is due to an issue in how Composer handles installation of composer-plugin type packages, and ensures the latest version of the package is used during the upgrade process. We are working to improve this process in future releases.

Next, run composer update to pull in the latest version of the packages.

This will generate a new composer.lock file. Both the composer.json and composer.lock should be committed to version control, and deployed.

Any upgrade will usually require some modification to your project (for example, deprecated APIs, new features you may want to implement). Altis is conservative about breaking backwards compatibility. Any known issues will be prefixed with "BREAKING: " in the version release notes.

Upgrade Guides