We had to find a way to ensure that your designs will work across any number of devices, without requiring you to create different versions for each aspect ratio.

We elected to support the three most popular aspect ratios: 4:3, 16:9 and 3:2. 

When you create slides for a new showcase, you’re going to want to pick the aspect ratio that you think will be in the hands of most of your users. These users will have a pixel-perfect fit, with your showcase designs taking up their entire screen.

If a user views your showcase on a device with a different aspect ratio, they’ll still have a pixel perfect experience (as in, it won’t stretch or distort) but they’ll have some black space around the edges. This is called "Letterboxing" if you're up with the lingo. 

Ratios: 

  • If your users are mostly going to use Showcase on iPads, use our 4:3 template, and design your slides at 2048 x 1536 pixels.
  • If your users are mostly going to use Showcase on popular Android devices, iPhones, via our Chrome app, or on early Windows devices, use our 16:9 template, and design your slides at 2048 x 1152 pixels.
  • If your users are mostly going to use Showcase on late model Windows devices, like the Surface Pro 3, use our 3:2 template, and design your slides at 2048 x 1365 pixels.

PPI: 

If you're used to designing for print, you might be wondering what resolution, or DPI, you should be using in your showcase designs. The nice news is that when designing for showcase slides, the resolution doesn't matter nearly as much as the pixel dimensions above. As long as you are at the minimum resolution of 72ppi for any PNGs you export, you should be absolutely golden. 
If your images are turning out large and you want to save some space, we use and recommend ImageOptim for compressing images.
If size is still a concern, you might like to consider making a "non-HD" version of your showcase - you can find the HD toggle as a checkbox in the "New blank showcase" dialog.