The best alternatives to NinjaMock are Balsamiq, Free Device Mockups, and Mockup World. If these 3 options don't work for you, we've listed a few more alternatives below.
What do you think of NinjaMock?
Postman Recorder by DevTools— Export Postman APIs from browser
Imagefactory.io harnesses the full power of 3D software to produce unique, personalised, photo-real images for your business. You can inject names or words into pictures, or project images onto products.