Why choose PNG for iPhone photos
HEIC photos from iPhones cannot be opened by many programs. Converting to JPG is fine for sharing, but if you want to edit, annotate, cut out or reuse the photo in designs, PNG is better: it keeps every pixel without adding new compression loss each time you save.
What happens when you convert
Each HEIC photo is decoded in your browser and saved as a PNG with the same width, height and colours. Hidden details such as GPS location and camera model are not copied. Several photos can be converted at once and downloaded together.
File size to expect
PNG photos are large — often five to ten times the size of the HEIC, and much larger than a JPG. That is the price of lossless quality. For simple sharing, use HEIC to JPG; for editing and design work, PNG is worth the space.
Common problems and how to fix them
The PNG is too big to upload: use HEIC to JPG or compress with Compress Image. A Live Photo lost its motion: only the still picture is converted. A photo appears sideways: rotate it with Rotate Image.
Good habits
Keep your original HEIC photos, convert to PNG only the photos you will edit, and export the finished design as JPG for sharing.