JSON (JavaScript Object Notation) files are not animated images. Or anything like an animated image file. One can't simply "watch them". They need a browser, or similar environment, to operate and often exterior objects to manipulate.
JSON files are strings of code which contain instructions for other, exterior, objects (objects which may be image files).
Basically a JSON file may tell objects how to move which may result in those objects appearing to be animated. However, that is quite different than an image moving on its own like in the GIF format.
JSON is more closely related to Javascript in nature than to any image format.
If you are familiar with animations in Cascading Stylesheets (CSS), the concept is similar... the code/markup merely controls how elements are animated, but rarely does it create the actual elements.