According to iOS’ Photos application, I’ve taken 73,281 photos over the past 14 years of owning an iPhone.
Each one of those images doesn't just contain the photo you see as you scroll through the Photos app — it contains a wealth of information stored encoded directly into the image file itself. It details useful metadata such as where the photo was taken (so that you can view your photos on a map at a later date), the time and date the image was taken at, which lens and zoom levels were used, the exposure, ISO, and aperture, amongst many others.
There are many, many tools for viewing this information. Whichever app you use to manage your photos will display this metadata alongside the image, such as in iOS 16 here:
This metadata is called EXIF (Exchangeable Image File Format) and is stored inside of the photo files themselves, appearing right at the start of the image (before any image data appears). If we inspect the contents of a JPEG photo directly exported from an iPhone, we see the EXIF data marker (FFE1) appear directly after the JPEG Start of Image marker (FFD8):
You‘ll be pleased to know this piece won't be spent going over every byte in the image above. Instead, we’ll be looking into what a photo contains, and the various ways in which we can display, query, and interact with the data therein.
What‘s in a photo?
The following visualization shows the vast amount of information stored within a single image. Feel free to pick from the curated examples from my personal photo library, or select your own image to view the EXIF data stored. Note that any images selected remain client-side and never leave your web browser. Client-side EXIF parsing is handled by the ExifReader library by Mattias Wallander.