This short blog post explains some differences between Contentstack hosting and external hosting of custom user interface extensions to its headless content management system.
As described in the following blog post, you can extend Contentstack with three types of user interfaces: custom field types (at the field level), custom widgets (at the entry level), and dashboard widgets (at the global level).
Hosted by Contentstack
If you choose External hosting when you define a UI extension, then you need to enter the URL of your UI extension, which you must deploy to a web host. Contentstack loads the extension URL into something like an <iframe> within the larger user interface. For development and testing, you can use localhost in the URL of the UI extension. For production, use a URL that is available to all CMS users. With external hosting, you can use an application server such as ASP.NET to generate HTML, handle HTTP posts, and otherwise. This code fits more naturally into a source code management system.