Please see this thread: https://developer.apple.com/forums/thread/651461
(looks like it’s only possible to get the size on submission)
jords
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When will the App Clip cards actually work (I mean the pop up with the image, title, subtitle and action button)?
After you’ve uploaded and set them up in App Store Connect.
After a build has been approved within TestFlight.
Only after the app has been approved and in the App Store.
Thanks
You can setup multiple app clip triggers in App Store Connect (not live on App Store Connect at the time of writing.) Each of these can have it’s own app clip card (image, title, subtitle and action button label.) You can only have one app clip target in your app. But you can respond to different user activities on invocation and setup different UIs in your app depending on the trigger (URL) that caused the open.
If your app clip triggers come from Apple Maps then your app clip icon can be customised based on the Apple Maps listing associated to that physical location, this happens automatically. Otherwise your app clip icon will be based off your full app icon.