Apple Watch resolutions and other interesting tidbits disclosed in developer tools

Apple Watch (Watchkit teaser 001)

Apple has left many questions unanswered regarding its upcoming smartwatch following its September unveiling. Representing a brand new form factor for iOS, the fashionable wrist-worn accessory sports a Retina panel which Apple bills as an “incredibly high pixel density” screen laminated to a machined and polished single crystal of sapphire (strengthened Ion-X glass on the Sport collection).

With today’s release of the official Apple Watch software development kit (SDK), watchful third-party developers have scanned the files in search of interesting tidbits and discovered references to pixel resolutions for both the 38mm and 42mm high Apple Watches, in addition to other previously unknown details worth mentioning.

The smaller 38-millimeter high Apple Watch will come outfitted with a 272-by-340 pixel resolution screen. The larger 42-millimeter device rocks a 312-by-390 pixel resolution Retina display.

I wanted to use the above values to calculate the exact pixel density of Apple Watches using the IsThisRetina web tool, but couldn’t because neither Apple nor the developer tools mention the exact Apple Watch screen sizes.

Apple Watch screen sizes (image 001)

Given Apple labeled the smartwatch’s screen as Retina-class, we can pretty much assume that an average human eye wouldn’t be able to discern the individual pixels when staring at the Apple Watch from normal viewing distances (that’s Apple’s unofficial definition of a Retina display).

San Francisco font

Other interesting findings:

  • The system-wide Apple Watch font called San Francisco (pictured above) supports Dynamic Type, an iOS technology that automatically adjusts the letter spacing and line height dynamically for maximum readability.
  • Developers can supply their own fonts, but won’t be able to take advantage of Dynamic Type should they do so and instead must optimize for readability themselves.
  • Watch apps are downloaded using the App Store on your iPhone, iPad, iPod touch or iTunes on your Mac or Windows PC. There’s no such thing as a dedicated App Store running directly on the Apple Watch.
  • Initially, third-party Apple Watch apps created using the Apple WatchKit are going to require a connected iPhone to function because much of the processing happens on the iPhone, not the Apple Watch. Actually, only storyboards and user interface resources are transferred to the Apple Watch.
  • Starting later next year, developers will be able to create fully native apps for Apple Watch – a feature no one saw coming before next summer.
  • Apple Watch icon sizes are as follows:
    • Notification center icon: 29-by-29 pixels (38mm Apple Watch) and 36-by-36 pixels (42mm Apple Watch).
    • Long look notification icon: 80-by-80 pixels (38mm Apple Watch) and 88-by-88 pixels (42mm Apple Watch).
    • Home screen/Short Look icon: 172-by-172 pixels (38mm Apple Watch) and 196-by-196 pixels (42mm Apple Watch).
  • Developers provide icons as full-bleed square images using the given dimensions and the system applies the circular mask automatically.
  • Maps embedded in third-party Apple Watch apps are static snapshots and not interactive within the app. Tapping the map takes the user to the Maps app.

Apple Watch (Watchkit Framework, slide 001)

  • Apple Watch does not support multi-finger gestures such as pinches although developers can add gesture recognizers to their apps. Out-of-the-box gestures supported across the system include:
    • Vertical swipes scroll the current screen.
    • Horizontal swipes display the previous/next page in a page-based UI.
    • Left edge swipes navigate back to the parent interface.
    • Taps indicate selection or interaction.
  • Notifications are provided in two forms:
    • Short Look: Provides a minimal amount of information to protect user privacy. A Short Look appears when a local or remote notification comes in and automatically disappears when you lower your wrist.
    • Long Look: Provides detailed information and more functionality after tapping a Short Look or when your wrist remains raised. Long Look notifications can optionally provide a dynamic interface and custom graphics and branding. The system automatically provides up to four action buttons in the Long Look interface (in addition to the always-present Dismiss button), based on the notification’s category. A Long Look notification does not disappear when one’s wrist is lowered  and must be actively dismissed by the user.
  • Subtle UI animations come in two forms:
    • Canned: Basically animations using a sequence of static images that can be presented quickly to the user at high frame rates.
    • Dynamic: Developers can also create animations programmatically, but Apple notes a dynamically animated interface adds a delay before playback can begin because the assets must be pre-rendered on an iPhone and transferred wirelessly to the Watch.

Just a quick though: because the first wave of Watch apps will do all the heavy lifting on an iPhone and stream results and UI back to the Apple Watch, using it may and will affect your iPhone’s battery life.

And those apps that use dynamic UI animations that get rendered on an iPhone may stop running if your iPhone isn’t present or the wireless connection has been disrupted. This won’t be much of a problem once Apple starts accepting native Watch apps later next year that run directly on the smartwatch hardware.

On the flip side, because all the processing happens on your iPhone you may not necessarily need to upgrade Apple Watch every year.

Apple Watch (Messages, Emoji)

In term of the guiding principles behind Apple Watch development, I deem the following excerpt from the official documentation the best summary of Apple’s approach to smartwatch user interfaces:

“A Watch app complements your iOS app, it does not replace it,” reads the document. “If you measure interactions with your iOS app in minutes, you can expect interactions with your Watch app to be measured in seconds. So interactions need to be brief and interfaces need to be simple.”

You can download the Apple Watch’s San Francisco font right here.

The official Apple Watch Human Interface Guidelines document is available through Apple’s website for developer resources here.

And if you’re really feeling like coding today, feel free to take a look at Apple’s official WatchKit Programming Guide.

More information is available at