You copy a folder of iPhone photos to a Windows laptop, double-click the first one, and get a prompt to visit the Microsoft Store. You attach the same photo to a job application and the upload form says the file type is not allowed. You email it to a relative and they reply that it shows as an attachment nobody can open. The photo is fine. The format is the problem.
iPhones save photos as HEIC by default, and HEIC is a format that Apple devices handle perfectly while a large part of the rest of the software world does not. JPG is the opposite: older, less efficient, and readable by nearly everything with a screen. This guide explains what separates the two, why HEIC files get refused, what changes when you convert one, and which conversion fits which job.
TL;DR: HEIC is the High Efficiency Image Container, a HEIF file (ISO/IEC 23008-12) whose photo is compressed with the HEVC codec. It stores a photo in roughly half the space of a JPG, but Windows often needs paid extensions to open it, Chrome, Edge and Firefox do not display it, and many upload forms reject it. Converting to JPG fixes compatibility at the cost of a second lossy compression. The HEIC to JPG converter does it client-side, nothing uploaded, free, no signup; use HEIC to PNG for a lossless copy or HEIC to PDF to put photos in one document.
What is a HEIC file?
A HEIC file is a still image stored in the High Efficiency Image File Format (HEIF) and compressed with High Efficiency Video Coding (HEVC). The two names describe two layers. HEIF is the container, standardized by MPEG as ISO/IEC 23008-12. HEVC is the codec that squeezes the pixels, published by the ITU as Recommendation H.265 and also used for 4K video. A HEIF file whose images are HEVC-coded gets the .heic extension; the broader .heif extension covers the same container with any supported codec.
Apple made HEIC the iPhone camera's default in iOS 11, released in 2017, under the setting called High Efficiency. Apple's own support article on HEIF and HEVC media covers the switch and how shared photos are handled. Many Android phones can also shoot HEIF, though most ship with JPEG as the default.
The container is more flexible than a JPEG. HEIF is built on the ISO Base Media File Format, the same box structure as MP4, so a single file can hold a primary image plus extra items: thumbnails, depth maps from portrait mode, image sequences from bursts, and metadata blocks. That flexibility is part of why HEIC support is harder to add than JPEG support.
What is a JPG file?
A JPG file is a photo compressed with the JPEG method defined in ITU-T Recommendation T.81, approved in 1992, and usually wrapped in the JPEG File Interchange Format described in ITU-T T.871. JPEG splits the picture into 8x8 pixel blocks, converts each block into frequency components with a discrete cosine transform, and throws away the fine detail the eye is least likely to miss. The quality setting controls how much is thrown away.
JPG and JPEG are the same format. The three-letter extension exists because early Windows file systems limited extensions to three characters, and both spellings survived.
JPEG's advantage is not technical. It is thirty years of universal support: every browser, phone, operating system, office suite, printer driver, photo kiosk and web form reads it.
HEIC vs JPG: how do they compare?
The short version is that HEIC wins on storage and capability, and JPG wins on compatibility. Here is the fuller comparison for everyday photos.
| Attribute | HEIC | JPG |
|---|---|---|
| Specification | ISO/IEC 23008-12 container, HEVC (H.265) codec | ITU-T T.81 codec, T.871 (JFIF) container |
| Released | ISO standard published 2017, iPhone default since iOS 11 | 1992 |
| Compression | Lossy, HEVC intra-frame coding | Lossy, 8x8 block DCT |
| Typical size for the same visible quality | Often around half of a JPG | Baseline |
| Color depth | 8 bits per channel, higher depths allowed | 8 bits per channel in practice |
| Transparency | Supported by the format | None |
| Images per file | Several, plus depth maps and thumbnails | One |
| Opens on Windows without add-ons | Often not | Yes |
| Displays in Chrome, Edge, Firefox | No | Yes |
| Accepted by upload forms | Frequently refused | Almost always accepted |
| Best use | Storing photos on Apple devices | Sharing, uploading, printing |
Two rows deserve a caution. The size saving depends on the photo: a detailed scene with foliage compresses differently from a portrait against a plain wall, so "around half" is a typical figure, not a guarantee. And HEIC's support for transparency and higher bit depths does not mean an iPhone photo uses them. Camera photos are opaque, 8-bit pictures either way.
Why won't my HEIC photos open?
HEIC files fail to open because the software trying to read them has no HEVC image decoder. The container is readable, but the pixels inside are coded with a codec that many programs never implemented. There are a few distinct reasons that happens.
Patent licensing. HEVC is covered by patents held by several licensing pools, and a company shipping an HEVC decoder may owe fees. Microsoft's response was to move HEVC support out of Windows itself and into a Store add-on. On many Windows 10 and 11 machines, opening a HEIC means installing the HEIF Image Extensions plus the HEVC Video Extensions, and the HEVC one usually costs a small fee. A work laptop where you cannot install anything simply cannot open the file.
Browsers. Chrome, Edge and Firefox do not display HEIC images. Safari added support in recent versions, which is why a photo can look fine on a Mac and break on the PC next to it. Any web app that shows your uploaded image back to you in the page runs into the same wall, so developers often block the type at the upload form.
Allow-lists. Visa and ID portals, job sites, marketplaces, print services and older content management systems check the extension against a short list, commonly .jpg, .jpeg and .png. A HEIC is refused before anyone looks at what is inside.
Older software. Photo editors, office suites and scanners released before 2017 predate the format. Some newer ones still skip it.
There is one more case worth knowing: a file named .jpg that will not open anywhere may still be HEIC inside. Renaming a file changes its label, not its contents. You can check by looking at the first bytes.
How can you tell a HEIC from a JPG without trusting the extension?
Read the first twelve bytes. Every HEIF file starts with an ftyp box that names its brand, and every JPEG starts with the bytes FF D8 FF. On macOS or Linux, xxd shows this directly:
$ xxd -l 12 IMG_4127.HEIC
00000000: 0000 0018 6674 7970 6865 6963 ....ftypheic
$ xxd -l 12 holiday.jpg
00000000: ffd8 ffe0 0010 4a46 4946 0001 ......JFIF..
The HEIC shows ftyp followed by the brand heic. Other HEVC brands you may see are heix, hevc and hevx, and a generic HEIF may list only mif1. An AVIF file uses the same ftyp structure with the brand avif, which is why an AVIF can be mistaken for a HEIC: same container, different codec. The comparison of AVIF against WebP and JPG covers that format.
This is also how the Toolz converters decide what a file is. They read the leading bytes rather than the name, so an iPhone photo renamed to .jpg is still recognized as HEIC and converted into a real JPG. If you drop a genuine JPEG onto the HEIC page, it is turned away with a pointer to the converter that handles it, because each pair page takes only its own source format.
What happens to a photo when you convert HEIC to JPG?
Converting HEIC to JPG decodes the HEVC-compressed photo into plain pixels and then compresses those pixels again with JPEG. Four things are worth understanding before you convert a camera roll.
Quality drops slightly. Both formats are lossy, so the JPG is a second approximation of a picture the phone already compressed. At a quality setting of 90 the difference is very hard to see in normal photos. No conversion recovers detail the camera discarded, so the JPG will never look better than the HEIC.
The file usually gets bigger. JPEG needs more bytes than HEVC to hold the same detail, so a 2 MB iPhone photo commonly comes out larger as a JPG at high quality. Lowering the quality brings the size down when you need to fit under an upload limit.
Metadata is not carried over. In the Toolz converter the photo is decoded to pixels and re-encoded through a canvas, so EXIF fields such as the capture date, camera settings and GPS location are not written into the JPG, and neither is the embedded color profile. When you share a photo publicly, the missing location is a privacy gain. When you are archiving, keep the original HEIC.
Extra images stay behind. When a HEIC holds more than one image, the primary image is converted and a note under the result says how many images the file contained. The video half of a Live Photo is stored as a separate file, so it is never part of the conversion.
HEIC to JPG, PNG or PDF: which conversion should you use?
Pick the target by where the photo is going next. JPG is the default for sharing, PNG is for editing without a second lossy step, and PDF is for handing over several photos as one document.
| You need to | Convert to | Why | Tool |
|---|---|---|---|
| Upload, email, print or open on Windows | JPG | Universal support, sensible file size | HEIC to JPG |
| Edit, retouch or composite the photo | PNG | Lossless, no second round of JPEG artifacts | HEIC to PNG |
| Submit receipts, IDs or a set of photos as one file | One page per photo, one attachment | HEIC to PDF | |
| Get WebP, GIF, an icon, or mix formats in one batch | Any | One page reads many sources | Image Converter |
The size difference between JPG and PNG is large. In a test with a small 320x240 HEIC, the JPG output was 6,921 bytes and the PNG was 74,410 bytes, more than ten times larger for the same pixels. PNG stores every pixel exactly using lossless compression defined in the W3C PNG specification, and exact storage of a photograph costs space. That is a fair trade for an editing master and a poor one for an email attachment.
For everyday sharing, convert your iPhone photos to JPG. The Quality slider runs from 10 to 100 and starts at 90; drop it to around 70 or 80 when files have to squeeze under a size limit.
When a photo is headed into an editor, HEIC to PNG gives you the decoded pixels with nothing further thrown away, so every later save starts from the best copy available.
When a form wants one document, the HEIC to PDF converter puts each photo on its own page in the order shown. Photos are embedded as JPEG at 92% quality to keep the PDF a sensible size, or as PNG if an image has transparency. You can fit each page to the photo, or use A4 or US Letter, where a landscape photo turns the page to landscape. The output is a standard PDF as specified in ISO 32000-2, so any reader opens it.
When the job is broader, the Image Converter reads HEIC alongside JPG, JFIF, PNG, WebP, AVIF, GIF, BMP, ICO, TIFF, PSD, SVG, CR2, DNG and PDF, and writes JPG, PNG, WebP, GIF, ICO, PDF or SVG. It is the right page when a folder mixes iPhone photos with screenshots, or when you want a HEIC as WebP for a website.
How does client-side HEIC conversion work?
Client-side conversion means the photo is decoded and re-encoded inside the browser tab, and the file never leaves your device. For HEIC that takes one extra step, because the browser cannot decode HEVC images on its own.
- The page reads the first bytes of each file and confirms the HEIF brand.
- The first time you convert a HEIC in a tab, the page downloads a decoder: libheif, an open source HEIF library compiled to WebAssembly, about 470 KB compressed. Pages that never see a HEIC never download it.
- The decoder runs in a Web Worker, a background thread, so the page stays responsive while a large photo decodes.
- The decoded pixels are drawn to a canvas and encoded as JPG or PNG by the browser, or embedded into a PDF.
- You download each file, or the whole batch as a ZIP.
Because of step 2, the first photo in a batch takes a few seconds longer than the rest. If the decoder download fails, the row says so and pressing Convert again retries it.
What are the limits, and what errors can you hit?
The limits exist to stop a browser tab from running out of memory, and each one produces a specific message rather than a frozen page.
- HEIC files over 100 MB are refused before they are read.
- Images over 100 megapixels are refused. A 12 MP iPhone photo at 4032x3024 is far below that, and so is a 48 MP photo.
- A decode that runs longer than two minutes is stopped, and the row offers a retry.
- A damaged or truncated file gets a message saying it could not be read. Photos cut short by an interrupted transfer are the usual cause.
- A daily conversion limit applies per tool. The tools are free, no signup, and there is no watermark.
If a file is refused as not being HEIC at all, look at its first bytes as shown above. It may be a JPEG or PNG with a .heic name, in which case it probably opens already, or it may be an AVIF, which has its own converters.
How do you stop an iPhone saving HEIC in the first place?
Change the camera format. On the iPhone, open Settings, then Camera, then Formats, and choose Most Compatible. New photos are saved as JPEG from then on, and they take more storage. Photos already taken stay HEIC.
A middle path keeps HEIC on the phone and delivers JPG to computers. In Settings, then Photos, under Transfer to Mac or PC, choose Automatic. Photos copied to a computer over a cable are then converted as they transfer.
Neither setting helps with the HEIC files you already have on a PC, in a shared folder or in an email. Those still need converting.
Should you keep HEIC or switch to JPG?
Keep HEIC for storage on Apple devices and convert copies when a photo leaves them. That gives you the smaller files and the extra data, such as depth maps and full metadata, in your library, and a universally readable JPG wherever compatibility matters.
Switch the camera to Most Compatible if you regularly move photos to Windows machines, work with software that predates HEIC, or upload to services that refuse it. The storage cost is real, but so is the time spent converting.
For web publishing, neither is the best choice. Photos on a website are usually smaller as WebP or AVIF, both of which current browsers display. The guide to what WebP is and why saved images come out as .webp explains that format, and the image tools hub lists every converter in the set.
Alternatives to an online HEIC converter
A browser page is not the only way to convert HEIC, and on some machines another route is quicker.
On a Mac, Preview opens HEIC natively. Open the photo, choose File, then Export, and pick JPEG. For many files at once, select them in Finder and use Quick Actions, then Convert Image.
On Windows with the HEIF and HEVC extensions installed, the Photos app can open a HEIC and save a copy in another format. Without the extensions, it cannot.
On the command line, ImageMagick and libheif's own heif-convert tool convert HEIC when they are built with HEIF support:
heif-convert IMG_4127.HEIC IMG_4127.jpg
The advantage of a client-side converter is that it needs no installation and no admin rights, works the same on any operating system, and keeps the photos on your device. The command line wins for scripting thousands of files on a server.
