## Content Type Changes
Content types are defined in the [Content Type Editor](🔗) or using the [Content Type Management API](🔗).
Users with [Site Developer](🔗) privileges can access the content type editor in the _Content_ app: select _Content types_ from the _Documents_ drop-down.
The Content Type Management API requires an [authorization token](🔗) which users with Site Developers privileges can obtain in the _Setup_ app.
You can create new content types, adjust existing ones, or manage “field group types”, i.e. composite structures of fields for grouping and reuse in multiple content types.
When making changes to content types, be careful about existing content. Changing the content type definitions will affect the output of the [Delivery API](🔗), which is consumed by the front-end. Existing document fields could go missing, and the front-end may no longer be able to render a proper experience.
To ensure that content type changes can be tested before applying them to live site content, they must be associated with a developer project (in the _Projects_ app) and go through the project review lifecycle. Only a single active developer project can include content type changes at one time, to avoid conflicting changes.
To enable content type changes within a development project, check the _Includes content type changes_ checkbox when creating a new project or in the _Project info_ tab of an existing development project:
Content type changes can be tested by creating new documents based on the affected content types in the context of the developer project. The content editor and site preview will adjust based on the content type model that is appropriate for the selected project.
Note that currently, once a new content type is merged to the live site configuration as part of a developer project, it can no longer be deleted.