HEIF is the container HEIC lives in, read here and not written. HEIC is what an iPhone writes unless you tell it not to: HEVC compression inside an ISO container, about half the size of the JPEG it replaced. ImageMagick sits between the two, and this page says exactly what happens to a HEIF file on the way to becoming a HEIC one.
What runs when a HEIF file becomes HEIC
ImageMagick 6.9.12, on a machine we rent and watch. Your HEIF file is uploaded once, ImageMagick runs once, the HEIC comes back, and neither file is kept. HEIF to HEIC is one of the 3649 pairs that engine was probed on with a real file, which is why it has a page here and why the pairs the probe could not prove do not.
What survives from the HEIF into the HEIC
The pixel dimensions of your HEIF file. The HEIC comes out the size the HEIF went in, because nothing on this path resizes anything.
Transparency. HEIF and HEIC both carry a real alpha channel, so a cut-out sent as HEIF is still a cut-out as HEIC.
What HEIF to HEIC costs you
Every frame of the HEIF but the first. HEIF can hold an animation and HEIC cannot, so frame one is what comes back. The alternative would be one numbered HEIC file per frame and no single answer to hand you.
Exactness. HEIC is a lossy encoding, so the file you get back approximates the HEIF you sent. The artefacts appear once and never come out again, which is why converting the HEIC back to HEIF afterwards restores nothing.
Where HEIF and HEIC files come from
HEIF. The container standard; HEIC is the name it goes by when the picture inside is HEVC. Read here and not written, because the write alias is not wired on the engine and pretending otherwise would hand you a file under the wrong name.
If a model is going to read the HEIC
A HEIC file is pixels, and pixels are expensive for a model to read. Handed this HEIC, an assistant spends its budget looking at the picture rather than reading it, and it will paraphrase what it thinks it saw. If your HEIF is mostly words, the useful move is to pull the text out of it, not to change which picture format holds it.
HEIF to HEIC, measured rather than promised
Running HEIF to HEIC against the real engine with a real file, ImageMagick wrote 486 bytes of HEIC in under a tenth of a second, machine otherwise idle. That is one HEIF file on one day and not an average, which is why the number is given together with the file that produced it.
The HEIF to HEIC verdict was reached by a format signature, meaning at least four bytes unique to the format were found at the right offset. Which check was used matters, because they do not all prove the same thing, and a status code of 200 proves nothing whatsoever about whether the HEIC file has anything inside it.
The same HEIF file, sent somewhere else
Other outputs the probe measured out of a HEIF file, so the cost of choosing HEIC can be read against something. Sizes do not compare across engines, because each family was probed with its own HEIF witness file.
HEIF to PDF: 94,782 bytes in under a tenth of a second, verified by a format signature.
HEIF to JPG: 1,666 bytes in under a tenth of a second, verified by a format signature.
HEIF to PNG: 1,403 bytes in under a tenth of a second, verified by a format signature.
HEIF to WEBP: 416 bytes in under a tenth of a second, verified by a format signature.
HEIF to GIF: 2,918 bytes in 0.1 seconds, verified by a format signature.
HEIF to TIFF: 90,264 bytes in under a tenth of a second, verified by a format signature.
Other ways into HEIC, and what they measured
Among the published routes into HEIC, HEIF is the eighth largest output of the 10 measured. The witness files differ, so this ranks the probe run and not your document.
ICO to HEIC: 807 bytes in 0.1 seconds.
SVG to HEIC: 1,009 bytes in 0.1 seconds.
TIFF to HEIC: 481 bytes in under a tenth of a second.
WEBP to HEIC: 579 bytes in under a tenth of a second.
PNG to HEIC: 481 bytes in under a tenth of a second.
What we will not pretend about HEIF to HEIC
A HEIF file over 25 MB is refused before the upload finishes rather than after it, so you do not wait for a rejection.
A HEIF to HEIC run that passes 30 seconds is killed, and the ImageMagick process is killed with it. A run left behind would sit on one of the machine's two cores until somebody noticed.
Until the end of August this machine could not read a HEIC at all, and reported the opposite. ImageMagick declared HEIC readable, but libheif carried only its AV1 plugins, which serve AVIF; the HEVC decoder was absent, and a HEIC decoded quietly as something else. The plugin was installed on the 30th, and that is the whole reason this pair exists.
The HEIF to HEIC proof used a file genuinely encoded in HEVC, and that detail is not pedantry: ImageMagick refuses to write HEIC and hands you a PNG under that name if you ask it to, so a HEIC forged for the test would have made a false result look like a true one. The HEIC it produced was 486 bytes, recognised by a format signature.
No text is read out of the HEIF anywhere on this path. Converting a picture to HEIC never turns it into words, whatever the picture happens to contain.
ImageMagick was not saturated at sixteen simultaneous conversions: it held 47.5 a second while latency moved from 0.22 s to 0.34 s, and the service memory did not move off 51 MB. That is the measured headroom behind HEIF to HEIC, not a marketing number.
One HEIF file at a time, chosen in the browser. There is nothing else to set up and nothing else on offer.
HEIF to HEIC: what people ask
What actually converts my HEIF file to HEIC?
ImageMagick does it, 6.9.12, on a machine we rent and watch. Not a browser trick and not somebody else service: the HEIF file is uploaded once, ImageMagick runs once, the HEIC comes back, and neither file is kept afterwards.
How long does HEIF to HEIC take?
On the file the probe used, ImageMagick took under a tenth of a second and wrote 486 bytes of HEIC. That is one real measurement on one real HEIF file, not an average and not a promise about yours: a larger HEIF takes longer, and past 30 seconds the run is stopped.
What do I lose going from HEIF to HEIC?
The one to know about first: Every frame of the HEIF but the first. HEIF can hold an animation and HEIC cannot, so frame one is what comes back. The alternative would be one numbered HEIC file per frame and no single answer to hand you.
My HEIF is animated. Will the HEIC be?
No. A HEIF can hold a whole sequence and a HEIC holds one image, so what comes back is the first frame. The alternative would be one numbered HEIC per frame, and there is no single file to hand you at the end of that.
Is HEIF to HEIC free?
There is a free allowance every month, and one HEIF to HEIC conversion costs half a credit against it. When the allowance runs out the tool says so and stops, rather than quietly handing you a worse HEIC.