Having authored quite a few of these, we'd love to share some tips where image size and desktop vs. mobile are concerned!
StepDemo is image-based; and because it uses images, it is not responsive. It'd be strange to resize a mobile app screenshot to a full desktop width, and even stranger to resize a desktop app to fit within a 320px-wide view (smartphone width).
This design decision to not resize assets was made to preserve legibility and clarity (images that contain lots of text quickly become illegible when resized). Now, there's no need to resize when viewing smartphone screenshots on desktop screens -- so how does StepDemo work when presenting desktop apps to smartphones?
When the Image is Larger than the ViewPort
If your image's size exceeds available screen real-estate, StepDemo's player will let your user 'slide around' during the demo. The player detects this and shows the user that they can 'move about' as the 'oversized' demo begins. This strategy preserves the image's original dimensions, preferring text-fidelity over "fitting everything without scrolling".
Got it. But I'm getting Larger Than Viewport Warnings for a Smartphone Screenshot!
Yes - let me explain this. In short: smartphone screenshots will yield more pixels than your phone can actually display (on the web).
If I take a screenshot of an app on my older iPhone 6s in portrait mode, it'll be 750 wide by 1334 tall.
When I transfer that directly into a demo and view it on my laptop - it'll be taller than its screen!
It's misleading because our phones are physically smaller than our monitors!
The fact is that phones perform something called 'UI Scaling':
The screenshot I took with my old iPhone 6S came out at 750 x 1334
The iPhone 6S has an actual resolution of 375 x 667
How do we make it all work!
Now that you understand the problem, it's easy enough to solve. Here are some working scenarios:
Scenario 1: I want my demos to fit on mobile screens.
The best option here is to utilize our Mobile Frame to create a Mobile Simulation Demo!
The Mobile Frame will only appear when the demo is played on desktop, ensuring your users will get the full mobile experience regardless of which method they choose.
Mobile Simulation Demo images will use the UI Scaling method, where uploaded screenshots must be at a higher resolution than what is shown to the user.
Images can be as tall as they need
Closing, when using the Mobile Frame, uploaded images must be wider than the outputted size, and they can be as tall as necessary.
Scenario 2: I am targeting desktop users, but am taking screenshots on an iPhone 8 Plus.
The iPhone 8+ has a resolution of 1080px wide and 1920px tall, and a maximum display width of 414px by 736px.
Since we're targeting desktop browsers, width won't be an issue. Most desktop screens are wider than 1080px. The screenshots from your iPhone 8+, will be 1080 by 1920.
You would be able to use your screenshots as-is...
...but... Unless your staff are all using Apple Cinema Displays, you may want to make your screenshots narrower to minimize up-down scrolling. By making them narrower and maintaining their aspect ratio, you will simultaneously reduce their height.