If the latest reports turn out to be true, it will be easy to spot the difference between an iPhone 12 and iPhone 13 because the notch at the top of the display is getting smaller.
As 9To5Mac reports, a couple of screen protectors alleged to be for the iPhone 13 have been posted by DuanRui on Twitter. They show a smaller cut out for the notch, which suggests Apple has reduced it in size. This isn't due to some miniaturization of the notch components, instead Apple moved the earpiece out of the notch and upwards into the phone bezel.
By making this design change, the notch remains the same height, but has been made narrower. When compared to the iPhone 12, it's roughly 30% narrower, meaning iPhone 13 owners will have a little bit more screen real estate. It also means there's probably a lot of app updates required following the launch of the new iPhone models to account for the change.
With the iPhone 13 not expected until around October, it's very unlikely to get a mention at the next Apple Event happening next week on April 20 (thanks Siri). We are likely to hear about new iPad Pros, hopefully a new Apple TV, and (finally!) AirTags.