Atomic is described as 'Work your way up from a blank canvas, or pull in designs from Photoshop or Sketch. Lay out your states and instantly animate between them, without coding a thing. Share your prototypes with anyone or view on any device via a humble' and is an website. There are more than 25 alternatives to Atomic, not only websites but also apps for a variety of platforms, including Mac, Windows, iPhone and Linux apps. The best Atomic alternative is Moqups, which is free. Other great sites and apps similar to Atomic are InVision, Principle, Presentator.io and Quant-UX.