Why iPhone photos will not open
Since iOS 11, iPhones have saved photos as HEIC rather than JPG. It is a genuinely better format, storing the same picture in roughly half the space. The problem is everything else: older versions of Windows, many websites, most upload forms and a great deal of software simply do not recognise it.
So a photo that looks fine on the phone that took it arrives as an unopenable file for the person receiving it. Converting to JPG solves that permanently, at the cost of a somewhat larger file. If the result is still too big for wherever you are sending it, the image compressor will bring it under an exact size limit.
Stopping it happening again
On your iPhone, open Settings, then Camera, then Formats, and choose Most Compatible. New photos will be saved as JPG from then on. Existing photos stay as they are, which is what this tool is for.
There is also a setting under Settings, Photos, at the bottom: Transfer to Mac or PC. Setting it to Automatic converts photos as they are copied off the phone.
Why this one does not upload your photos
Camera-roll photos are among the most personal files people have, and most HEIC converters ask you to send them to a company's servers. This one decodes them inside your browser using libheif compiled to run locally, so nothing is transmitted and there is no limit on how many you convert.
The trade-off is a 3MB download the first time, since the decoder has to reach your device. It is cached afterwards.
Turning several photos into one document
A common reason for converting HEIC is that a form wants a single PDF rather than a folder of pictures. If that is what you are doing, skip the conversion step entirely: the images to PDF tool reads HEIC directly and merges everything into one document in the order you choose.
If you need a format other than JPG, the format converter handles PNG and WebP as well, and accepts HEIC as input in the same way.
What HEIC actually is
HEIC stands for High Efficiency Image Container, and it is Apple's implementation of a standard called HEIF. Rather than storing a photograph the way JPG has since 1992, it borrows compression techniques from modern video encoding, which is why it fits roughly the same picture into half the space.
It also does things JPG cannot. A single HEIC file can hold multiple images, which is how Live Photos and burst shots are stored. It supports transparency, depth information used for portrait mode, and colour depths beyond what JPG allows. None of that survives conversion, which is worth knowing if you are converting a Live Photo: you will get the single still frame, not the motion.
Why Windows in particular struggles
Support depends on codecs that Microsoft licenses rather than includes. Windows 11 handles HEIC in many cases; older Windows 10 installations often do not, and will offer a paid extension from the Microsoft Store instead. That is why the same file opens for one person and not another, which makes it a confusing problem to diagnose over a phone call.
Android has supported HEIC since version 10, but many apps on it still do not. Web upload forms are the most common failure point of all, because they validate file types against a list written years ago.
When to keep the HEIC instead
- Storing your own archive — the originals are smaller and higher quality. Convert copies, keep the originals.
- Sending to another Apple device — it will open natively, and converting only makes the file larger.
- Editing professionally — HEIC preserves more colour information than JPG, so edit first and convert last.
Convert when the file is leaving your control: uploading to a form, emailing someone on Windows, or posting somewhere that rejects it.
What a converted file will look like
At quality 90, the two are visually identical in normal viewing. What changes is size: a 2MB HEIC typically becomes a 3 to 4MB JPG, because JPG is simply less efficient. That surprises people who expect converting to make files smaller. It does the opposite.
If the resulting JPG is now too large for what you are doing, use the resize option above, or run it through the image compressor afterwards to land under a specific limit.
Questions
Will I lose quality?
At quality 90 the difference is not visible in normal viewing. If you want no loss at all, choose PNG, though the files will be several times larger than the HEIC original.
Does it keep the date and location?
No. Converting drops the embedded metadata, including GPS coordinates and timestamps. That is usually an advantage when sending photos to strangers, but worth knowing if you rely on photo dates.
Can I convert hundreds at once?
There is no limit imposed here, but each photo is decoded by your device, so a very large batch takes time and a phone may run out of memory. A few dozen at a time is comfortable on a laptop.