Editlayer is a headless CMS that operates in a cloud. The content is saved to a JSON file.
You can use Editlayer for many purposes where you or your customer need to be able to edit the content. This is not only CMS needed for traditional websites' contents editing, although Editlayer works great for that too.
Editlayer is suitable for developers of all levels. Really the only requirement is that you understand what JSON is. It's a simple open standard file format for communication. After you have gotten to know JSON, you can pretty much use Editlayer.
You can give your clients access to edit the contents of the projects. They don't have to know anything beforehand, the content will be editable via a simple user interface.
Find more headless content management systems.