File Type Not Supported? Convert It to One That Works

Quick answer

Convert it, do not rename it

// Answer

Photographs go to JPG, screenshots and logos to PNG, documents to PDF. If it is an iPhone photo it is almost certainly HEIC, so use HEIC to JPG. If it is a photo saved as PNG, use PNG to JPG. If it is a pile of images that needs to be one document, use images to PDF. Changing the extension by hand does nothing useful, because the receiving system reads the contents, not the name.

Pick a target

What to convert to, and with what

What you have	Convert to	Tool
An iPhone or iPad photo (.heic, .heif)	JPG, or PNG if it must stay lossless	HEIC to JPG or HEIC to PNG
A photograph saved as PNG	JPG	PNG to JPG
Several photos that must be one document	PDF	Images to PDF
Several PDFs that must be one file	One PDF	Merge PDF
A whole camera roll of HEICs	JPGs, delivered as a ZIP	Batch HEIC to JPG
A HEIC you only need to look at	Nothing. Just open it	HEIC viewer

If the form also complains about size once the format is right, that is a separate problem with a separate fix: see file too large to upload.

The usual culprit

It is probably an iPhone photo

Apple devices capable of it record photos as HEIF and video as HEVC by default, rather than JPEG and H.264. The picture is the same and the file is considerably smaller, which is a real improvement — it simply arrived years after most upload forms were written, and a form that was told to accept JPG and PNG has no idea what a .heic is.

You have two options. Convert each photo as you need it, with HEIC to JPG, which also lets you drop the quality if the form has a size limit as well. Or stop the phone producing them: Apple's instructions are to "Open Settings, then tap Camera. Tap Formats, then tap Most Compatible", after which "all new photos and videos will now use JPEG or H.264 format" (Apple Support). That setting changes future photos only, so you will still need to convert the ones already on the phone. There is a longer walkthrough on stopping your iPhone taking HEIC photos, and one on what to do when a site refuses a HEIC.

The shortcut that fails

Why renaming the extension does not work

It is the first thing everyone tries. A file called photo.heic gets renamed photo.jpg, the file picker stops complaining, and for a moment it looks like a win. It is not one. The extension is a label attached to the name; the bytes inside are unchanged. Many systems read the first few bytes of a file to see what it really is, and a JPG and a HEIC do not begin the same way.

The reason the picker stopped complaining is worth understanding, because it tells you where the real check happens. A form can tell the browser which types it expects, but as Mozilla's documentation puts it, that hint "doesn't validate the types of the selected files; it provides hints for browsers to guide users towards selecting the correct file types", and "you should make sure that expected requirement is validated server-side" (MDN). In other words the greyed-out files in the picker are a courtesy. The decision is made later, on a machine you cannot argue with.

The best case for a renamed file is that it is rejected. The worse case is that it is accepted, stored, and then fails silently for whoever tries to open it — a passport photo that will not display in a caseworker's system, a product image that renders as a broken box.

Background

Why sites restrict formats at all

Three reasons, in rough order of how much the site cares.

Security. A file upload is one of the most reliably dangerous features a web application can offer. Restricting the accepted types to a short list of formats the site can parse safely removes a large amount of that risk in one line of configuration.
Whatever happens next. The file is rarely just stored. It gets resized, printed, put into a PDF, checked by a human, or passed to a system built in 2009. That chain has to be able to read it, and it is usually the oldest link that decides the list.
Predictability. A narrow list means every file in the system behaves the same way. It is a lot easier to support than "anything the browser can open this week".

None of which helps you at the moment of rejection, but it does explain why the list is short and why arguing with it is not an option.

Other causes

When it says "type" but means something else

Some rejections name the file type because that is the only message the developer wrote, not because the type is wrong. Check these before you convert anything:

The file is damaged. An interrupted download or a half-finished cloud sync leaves a file that is the right length in the listing and unreadable in fact. Open it on your own machine first. If it will not open there, converting it will not help.
It is zero bytes. Surprisingly common after a phone runs out of space mid-save. Nothing recovers this except the original.
It is password-protected. A locked PDF cannot be read by the site, so it fails whatever check comes first. You need to remove the password in whatever created it; no browser tool here will open a document you cannot open yourself.
It is an old Office format. The older .doc and .xls are completely different formats from .docx and .xlsx, despite the similar names. Re-save it from Word or Excel, or export it as PDF.
The extension is wrong already. Files renamed by a previous owner, or saved with the wrong "Save as type", declare themselves as something they are not. The receiving system is reading the contents and telling you the truth.

There is one more possibility worth naming: the form dislikes what is inside the file rather than its type. A photograph carrying GPS coordinates, camera serial numbers and a timestamp may have that data stripped by systems with a privacy policy to keep. Remove EXIF data shows you what your photo is actually carrying before you send it anywhere.

It was refused for its size instead: file too large to upload.
It was an email that objected: email attachment too large.
Every other reason a file gets refused: why was my file rejected.
Curious which format is actually smallest for your picture? The image format benchmark measures your own file rather than quoting an average.
All of this happens in your tab: how converting without uploading works.

FAQ

Frequently asked questions

No, and it usually makes things worse. The extension is a label; the contents are what the receiving system reads. Renaming a HEIC photo to .jpg produces a file that claims to be a JPG and is not one, so it either fails a stricter check or is accepted and then breaks something further down. Convert it properly instead.

The form has told the browser which types it expects, so the operating system dims everything else. It is a hint rather than a rule, and on most systems you can switch the picker to show all files. Doing so does not help: the real check happens after the upload, on the server.

JPG for photographs, PNG for screenshots, logos and anything that needs a transparent background, PDF for documents. Those three cover almost every form on the internet. If the form has an example or a template, match whatever that is.

Because iPhones and iPads shoot HEIF by default, which stores the same picture in considerably less space. It is a genuinely better format that arrived after most upload forms were written. You can convert each photo, or change the camera setting so new photos are taken as JPEG instead.

Then the format is probably not the problem. A file can be truncated by a failed download, password-protected, zero bytes after a sync error, or saved with an extension that does not match its contents. Try opening it locally first: if your own computer cannot read it, no website will either.

Last reviewed 2 October 2026

The form says your file type is not supported