Real-time comparison of expected and implemented design. Built into iOS simulator. Flawless App is a macOS tool, that allows you to compare design mockups with final result right inside iOS simulator. It helps easily spot visual differences between design and implementation. Check how accurate your implementation is using two powerful comparison modes: Split and Overlay. You can compare implementation in iOS simulator with any image file (png, jpeg, jpg, gif, tiff etc.) or even directly with Sketch file.