What is HEIC, and why do some websites reject it?

Quick answer

HEIC is the iPhone’s default photo format: an image encoded with HEVC and stored in HEIF (High Efficiency Image File Format). At about the same quality, the file is smaller than a JPEG and saves more space. The problem is that the upload forms of many registration systems, schools, and government websites only accept JPG or PNG, and some Windows PCs need extra support installed to open it, so you get a “format not supported” error. The fix is to convert to JPG before uploading, or switch the camera to Most Compatible so future photos are shot as JPG directly.

What is HEIC?

Since iOS 11, the iPhone has taken photos in HEIF (High Efficiency Image File Format) by default. HEIF is a container format; the image in an iPhone photo is encoded with HEVC, and that combination has the file extension .HEIC, while video uses HEVC (H.265). According to Apple, HEIF compresses better than JPEG, so it can keep the same quality while saving more storage on the iPhone and in iCloud Photos.

Every model from the iPhone 7 on can shoot in this format. In Settings, then Camera, then Formats, you will see two options:

• High Efficiency: shoots with HEIF/HEVC and saves more space (the default).
• Most Compatible: shoots with JPEG/H.264, with better compatibility; most computers and websites can open it.

What are the advantages of HEIC?

• Smaller files: for the same picture, HEIC is usually smaller than JPEG, so your phone and iCloud can hold more photos.
• More efficient compression: HEIC is also lossy, but needs less data than JPEG for the same quality.
• Smooth across Apple devices: iPhone, iPad, and Mac all support it natively, and syncing through iCloud Photos keeps the original format.

To understand why the same photo can get smaller, see How does image compression work?

Why do websites reject HEIC?

1. The upload form only accepts JPG and PNG

The upload fields on many registration, application, school, and government sites only allow .jpg, .jpeg, .png, and .pdf. These systems need to show a preview on the page, generate thumbnails, or pass the file to back-end checks, and HEIC has always had lower support on the web than JPG, so they simply do not accept it.

2. Some computers cannot open it

Macs have supported it natively since macOS High Sierra. On Windows it depends on the version and installed components, and some PCs need the HEIF extensions installed separately from the Microsoft Store to open it. If the person handling your application cannot open the file, it is as if they never received it.

3. Older systems and software do not support it

Older operating systems, photo editors, and internal company systems often only recognize long-established formats such as JPG and PNG.

When does the iPhone convert it for you automatically?

You do not always have to convert manually. Apple describes several cases where it converts to JPEG automatically:

• AirDrop, Messages, Mail: if the other person’s device does not support HEIF, the system may automatically share a JPEG.
• Importing to a computer by cable: with Settings, then Apps, then Photos, then Transfer to Mac or PC set to Automatic, photos imported to a Mac or PC may be converted to JPEG.

But web upload forms do not necessarily convert automatically; what actually happens depends on the browser and the site. If you pick a HEIC photo from your library, the site may receive it as HEIC, and a form that only takes JPG will block it.

Should you switch to Most Compatible?

Your situation	Recommendation
Photos mostly stay on iPhone, Mac, and iCloud	Stay on High Efficiency to save space
You often send to Windows PCs or company systems	You can switch to Most Compatible to skip converting
You only occasionally upload to registration or application sites	Stay on High Efficiency and convert to JPG when needed
Your phone storage is already tight	Stay on High Efficiency

Note that switching to Most Compatible only affects photos you take afterward; HEIC photos taken earlier do not turn into JPG automatically. To convert photos you have already taken, see How to convert HEIC photos to JPG on iPhone, which covers built-in methods such as the Files app and the iOS 26 Preview app.

Handle format and size together with PassSize

When an upload gets stuck, two problems often arrive together: it must be JPG, and it cannot exceed 2MB or 500KB. PassSize can:

• Convert HEIC to JPG or PNG, several photos at a time.
• Then compress to 500KB, 1MB, 2MB, or a custom size, and also limit the dimensions (for example 1200x1200).
• Understand rules typed the way sites write them, such as “1200x1200 to JPG” or “limit 2MB”.
• Do both conversion and compression on your phone.

A note: some sites check the file extension instead of the real format. Do not simply rename the file from .HEIC to .JPG; the contents have not changed, so the other side may still be unable to open it. Use a conversion tool to convert it for real.