How smartphones store image metadata
iPhone HEIC and Android JPEG both use EXIF, but the details — and defaults — differ.
iPhones store photos as HEIC (or JPEG in compatibility mode). HEIC is a container format that carries the same EXIF, IPTC, and XMP blocks as JPEG, plus depth maps for Portrait Mode and burst grouping. Apple writes surprisingly rich data: capture type, live photo pointer, HDR gain map references.
Android phones vary by manufacturer. Google Pixel writes clean EXIF plus a "Google" IFD extension for computational photography tags. Samsung adds an SEFT block for its own features. Both platforms tag photos with GPS by default when location permission is granted to the camera app.
The single biggest step you can take on either platform is to revoke camera location permission unless you actively want geotagging.