Contentstack

With the help of a JSON architecture and APIs supported by content delivery networks (CDNs), Contentstack is a headless CMS software that enables businesses to deliver personalized content experiences to audiences via various channels, such as mobile or web devices, augmented or virtual reality platforms, and the Internet of Things (IoT).

Administrators can set up role-based access permissions for adding, amending, publishing, or deleting content entries as well as modify or format photos for a particular device's display.

To offer individualized, multichannel digital experiences, Contentstack brings together business and technology teams from Enterprise, SMB, and Startup organizations

Contentful

One of the most popular and simple Headless CMS. It runs as a web service, so you have only to register an account to create a project. Contentful is very easy to use, stable and has a free version. In addition, there are lots of plugins and a package for working with this CMS.

But there are some shortcomings. First of all, it's a limitation of entities (models) and fields in the model. Also, like many Headless CMS services, the size of uploaded files is limited.

Despite the great popularity of Contentful, it could be a challenge to create even a small project due to limitations. Therefore, we recommend using it only for very simple projects.