When to pick PNG
PNG is lossless: every pixel of the decoded photo is kept exactly, with no JPEG blockiness. That helps when you plan to edit the picture further, or when a form or app insists on PNG.
The price is size. A PNG of a photo is often three to ten times bigger than a JPG. If you only need to share or upload, JPG is the better choice and you can switch with one click.
What HEIC is and why it won't open
HEIC (also written HEIF) is the photo format iPhones use by default. It keeps pictures sharp at about half the size of a JPG, but many Windows apps, older Android phones, email clients, print shops and upload forms can't open it.
A JPG opens almost everywhere, so converting is the quickest way to share or upload a photo. PNG also opens everywhere and never loses detail, but the files are much larger.
Private by design
Your photos are converted inside this page. Nothing is uploaded and the page cannot make network requests to other sites. Location, camera model and the date taken are not copied into the new file, so it is safe to share. Photos are turned the right way up, and if a HEIC file holds several pictures (a burst or the still from a Live Photo), the main one is converted.
Questions
Are my photos uploaded anywhere?
No. The conversion runs in your browser and the page blocks network requests to other sites, so your photos never leave your device.
Can I convert many photos at once?
Yes. Add as many as you like. They are converted one after another so your device stays responsive, and you can download each PNG or everything as a single zip.
Does the photo keep its location and date?
No. The new file is built from the pixels only, so GPS location and camera details are removed. That is useful for privacy, but it means the date taken is not kept either.
Why does a very large photo take longer or fail?
A 48 megapixel photo needs a lot of memory to decode. If a photo fails, close other tabs or convert it on its own.
Is PNG better quality than JPG?
A PNG does not lose any detail from the decoded photo, while a JPG is compressed. At High quality the difference is hard to see, and the JPG is far smaller.