Flawless App is an app with precisely one purpose: to make it easy for developers everywhere to make pixel-perfect layouts. It does this using an ingenious iOS Simulator injection to overlay images from your designers over your live application, so you can see the designs and your actual layouts side by side.
It’s important to stress up front that Flawless App does not modify your code or go near your final app, so there’s no performance degradation or chance things will go wrong for your users. Instead, it’s controlled by a small macOS menu bar app backed up by the simulator overlay – it’s the kind of thing you can leave running all the time if you wanted.
To get started, drag an image onto the Flawless App icon to have it loaded into your simulator. It supports JPEG, PNG, GIF, TIFF, and even Sketch files so you should be able to find something that works for you. That image then gets loaded into an overlay alongside your app, at which point you have three viewing options:
It’s hard to overstate how useful the split-screen mode is – you can see both your current layout and your target layout side by side, making it extremely convenient to see where you need to make changes. Flawless App can even output an animated GIF for you, making it easy to show others the current state of your work.
And that’s the entire app. It’s not trying to throw in lots of features, and it’s not trying to solve multiple different problems – it’s designed to do one thing, and it does it extremely well.
Flawless App is currently available as v0.8, so I wasn’t surprised to see a couple of bugs in there. The hotkeys, for example, allow you to change overlay mode using Cmd+Shift+R, at least in theory – in practice it didn’t work for me. The animated GIF support also didn’t work well for me, but this seems to be an issue specifically with landscape apps. I already emailed the Flawless team about these, and they responded in 15 minutes saying they are on the case.
Flawless App costs $30 for a lifetime license valid on two machines plus product support, but if you’re not sure there’s also a 14-day free trial. Such a low price with lifetime updates included makes Flawless App a steal – it will immediately save you time, while also helping you nail your layouts once and for all.
Flawless App 0.8
If you’re serious about making your user interface match the designs you were given, Flawless App is such an obvious purchase that I can’t imagine why you wouldn’t invest.
Paul Hudson is the creator of Hacking with Swift, the most comprehensive series of Swift books in the world. He's also the editor of Swift Developer News, the maintainer of the Swift Knowledge Base, and Mario Kart world champion. OK, so that last part isn't true. If you're curious you can learn more here.