Spark on iPhone Duo

Spark is optimized for iPhone Duo, the first foldable iPhone. Your inbox has more room now: open iPhone Duo, and your inbox and the open message sit side by side on the inner display. Close it, and Spark switches back to a single view on the outer display.
Spark works in every pose - closed, fully open, partially folded, seated, or standing - with the same actions and the same content in each one.

Note: These improvements work automatically. You don’t need to turn anything on in Spark Settings.

Prerequisites

Here’s what you need to use Spark on iPhone Duo:

iPhone Duo with iOS 27.1 or later
The latest version of Spark from the App Store

To check which version you have, see How to check your Spark version. If you have trouble updating, see Issues with installing or updating Spark.

How it actually works

When iPhone Duo is open, Spark uses the larger inner display to show two things at once:

your Inbox list on one side
the open message on the other

Tap any email in the list, and it opens right next to your Inbox, so you can move through your emails without going back and forth between screens.

When you fold the iPhone Duo closed, Spark returns to a single view on the outer display, just like on any other iPhone. Since both displays share the same aspect ratio, the experience feels continuous whether the iPhone Duo is open or closed.

Note: The side-by-side layout is part of Spark itself. It’s different from Split View, the iOS 27 feature that lets you open two different apps next to each other.

Reading, writing, calendar, and search adapt to the fold

The screens you use most reflow as you open, close, and partially fold iPhone Duo:

Reading: emails resize to fit the display you’re using
Writing: the composer adjusts as you open or fold the device, so you can keep writing
Calendar: your schedule makes use of the extra space on the inner display
Search: results adapt to the inner and outer display

When iPhone Duo is partially open, Spark keeps text, buttons, and dialogs clear of the folding region in the center of the inner display, so nothing you need to read or tap lands on the fold.
Settings and dialogs follow Apple’s guidelines too: sheets, alerts, and menus move the way they do in Apple’s own apps.

Spark in every pose

However you hold or place the iPhone Duo, Spark gives you the same actions and content. Only the layout adjusts:

Closed: a single view on the outer display, just like on other iPhone models
Fully open: your Inbox and the open message side by side on the inner display
Partially folded: screens reflow, and text, buttons, and dialogs stay clear of the folding region
Seated or standing: iPhone Duo propped on a surface; the layout adjusts, and every action stays available

Whether you’re triaging your inbox on the go or reading a long thread with iPhone Duo propped on your desk, everything works the way you expect