Systems and methods for developing user interfaces. User interfaces are previewed by including plugins in a preview user interface. A preview user interface includes a preview of a plugin in the context of a live user interface. The preview user interface is generated from preview web assets that are a copy of of the web assets used for the live user interface except for the plugin. The plugin is written to the preview web assets and the preview user interface can then be previewed as if the plugin were part of the live user interface. Once the plugin is approved, the plugin can be incorporated into the live user interface.