HEIC · Image formats
What image format do online forms accept?
JPG and PNG are safe on essentially every upload form ever written, and JPG is the safer of the two when the form does not say. GIF is often allowed. HEIC, WebP, AVIF, JFIF, BMP and TIFF are commonly rejected, and SVG is usually blocked deliberately rather than by oversight. Format is only half the problem, though: a great many rejections are actually file size limits, because a modern phone camera produces 3 to 12 MB images and plenty of forms cap uploads at 1 or 2 MB. If a form refuses your photo without naming a format, check the size limit before you convert anything.
The two formats that always work
JPG is the most widely supported image format in existence and the right default for a photograph, a scanned document, or a photo of yourself for an application. If a form lists what it accepts and JPG is on the list, use JPG.
PNG is the other safe choice, and the better one when the image contains text, sharp edges, or a screenshot. It is lossless, so nothing softens, but the file is substantially larger for a photograph — which matters when there is a size cap.
GIF is accepted more often than you would expect, largely because it has been around since 1987 and made it onto every allowlist. It is a poor choice for anything photographic, since it is limited to 256 colours.
What gets rejected, and why it is not your fault
HEIC is the most common cause by a wide margin. Every iPhone photo since iOS 11 is HEIC by default, and almost no upload form has been updated to take it. The file is fine; the form predates the format.
WebP and AVIF are the modern web formats. Most images on the web are now served as one of them, so "save image as" hands you a file that browsers display perfectly and upload forms refuse.
JFIF is an ordinary JPEG with an unfamiliar extension, produced by a Windows registry quirk. BMP and TIFF are old formats that are simply not on most allowlists, and TIFF files are usually far too large anyway.
The common thread is that forms decide what to accept from a list of extensions written years ago. Converting to JPG or PNG satisfies every one of them.
Size limits cause as many failures as formats
This is worth ruling out first, because the error messages read similarly and people spend a long time converting a file whose format was never the problem. A current phone camera produces images of 3 to 12 MB. Government portals, university applications and older marketplace systems frequently cap uploads at 1 or 2 MB, and some ask for far less.
Note the direction of travel: converting a HEIC to JPG makes the file larger, not smaller, typically by 1.5 to 2.5 times. If the rejection was about size, that conversion has made things worse. What helps is reducing the pixel dimensions, which cuts the file size roughly with the square of the scale factor.
What portals mean by their pixel and KB requirements
Application portals often specify something precise, such as a photograph of 200 by 230 pixels between 20 and 50 KB, and a signature between 10 and 20 KB. Those numbers are not arbitrary — they are sized for the printed document the system eventually produces — and they are usually enforced exactly.
Two things follow. First, resize before you compress: getting to 20 KB by crushing JPEG quality on a full-resolution photo produces a blurry mess, while resizing to the requested dimensions first gets you there at good quality. Second, ignore any instruction about DPI. Dots per inch is metadata that has no effect on a file uploaded to a form; only pixel dimensions and file size matter.
SVG is blocked on purpose
When a form rejects an SVG it is usually not an oversight. An SVG is a text file that can contain scripts, so accepting user-uploaded SVGs and serving them back is a well-known way to expose a site to cross-site scripting. Most platforms block the format deliberately rather than take the risk.
Convert vector artwork to PNG if you need transparency, or to JPG if you do not. Both are accepted everywhere, and both are what the form actually wanted.
Frequently asked questions
What is the safest image format to upload?
JPG. It is accepted by essentially every form ever built, and it keeps photographs small. Use PNG instead when the image has transparency or contains text and sharp edges.
Why does the form reject my iPhone photo?
Because it is a HEIC file, the default on every iPhone since iOS 11. Most upload forms accept only JPG and PNG. Convert it to JPG and it will upload.
The form says my file is too large. Will converting help?
Not on its own, and converting HEIC to JPG will make it larger. Reduce the pixel dimensions instead — file size falls roughly with the square of the scale, so halving the width and height cuts the size to about a quarter.
What does the portal mean by 20 KB to 50 KB?
A limit on the finished file size, enforced exactly. Resize the image to the pixel dimensions the portal asks for first, then adjust JPEG quality to land inside the range. Compressing without resizing gives a blurry image at the same size.
Do I need to set the DPI to 300?
No. DPI is metadata that affects printing, not files uploaded to a form. Only the pixel dimensions and the file size are checked.
Why will the form not accept an SVG?
Because an SVG can contain scripts, so most platforms block it deliberately as a security measure. Convert it to PNG or JPG.