303803 2025-12-08 18:53:25 -0800 PNG converted to HEIC on file upload seemingly not accepted by image/* wildcard 2026-01-08 07:45:39 -0800 1 1 1 Unclassified WebKit Images Safari 18 All macOS 15 RESOLVED FIXED InRadar P2 Normal --- 1 gizmo-bobcat6l karlcow gizmo-bobcat6l karlcow sabouhallawa webkit-bug-importer oldest_to_newest 2164313 0 gizmo-bobcat6l 2025-12-08 18:53:25 -0800 Since Safari 17, uploaded <input type="file" accept="image/*,image/heic"> converts PNGs or JPGs to HEIC first before uploading, even though the image/* should be enough for that media types to be accepted without conversion. Explicitly adding HEIC to that list (for historical reasons) does not mean it's the only or preferred format accepted, but Safari starts converting every other image type to it in such forms. MRE: https://jsfiddle.net/us1hdpzr/ Simply adding an explicit PNG mime type allows PNGs unconverted: https://jsfiddle.net/gk0b74uc/ (NB: This example still converts JPEGs or GIFs before uploading, for demonstration. This time to PNGs, as that's the first fully enumerated accept type in the list, so the tempImageNnNNnN.png from other formats is coerced into PNG in this instance.) For support it doesn't matter if the PNG is first in the order or not, it can be added well after the HEIC or after the wildcard: https://jsfiddle.net/8spartde/ — what matters in the order however, is what's the first non-wildcard accept type, to which the other ones get converted. Demonstrated by this order: https://jsfiddle.net/q3op1u6c/ which converts GIFs to JPEGs, being the first in the list. So the issue is not actually HEIC/HEIF specific per se, as just specifying a wildcard, and a full mime type like this: https://jsfiddle.net/hLxpmt2b/ also reproduces this problem, here coercing everything from GIF to HEIC to a PNG beforehand. It just seems related to the logic added some time ago to convert HEIC/HEIF files for compatibility reasons to other image formats. But the logic seems ending up too greedy, and doing conversions even in unexpected directions since then? 2164318 1 gizmo-bobcat6l 2025-12-08 19:02:47 -0800 Some previous work in that field: - Bug 213347 - Bug 292041 - Bug 219783 Other reports: - https://developer.apple.com/forums/thread/743049 - https://core.trac.wordpress.org/ticket/62447 (explicitly adding the mime due to https://issues.chromium.org/issues/375118901 …) 2164331 2 karlcow 2025-12-08 20:45:35 -0800 Different test cases: The script part is the same in all cases. <input type="file" multiple accept="CONTENT_TYPE_VALUE" id="file"> <p id="result"></p> <script> document.getElementById("file").addEventListener("change", (ev) => { document.getElementById("result").innerHTML = [...ev.target.files] .map((file) => file.name) .join("<br />") }) </script> Select A PNG as input # test case A: https://jsfiddle.net/us1hdpzr/ accept="image/*, image/heic" # test case B: https://jsfiddle.net/gk0b74uc/ accept="image/png, image/*, image/heic" # test case C: https://jsfiddle.net/8spartde/ accept="image/heic, image/png, image/*" # test case D: https://jsfiddle.net/q3op1u6c/ accept="image/jpeg, image/png, image/*, image/heic" # test case E: https://jsfiddle.net/hLxpmt2b/ accept="image/png, image/*" I'm adding a test case F # test case F: accept="image/*" on macOS 26.2 Safari - PNG =========== A: tempImagebLRNyk.heic B: webcompat.png C: webcompat.png D: webcompat.png E: webcompat.png F: webcompat.png Firefox - PNG ======= A: webcompat.png B: webcompat.png C: webcompat.png D: webcompat.png E: webcompat.png F: webcompat.png Chrome - PNG ======= A: webcompat.png B: webcompat.png C: webcompat.png D: webcompat.png E: webcompat.png F: webcompat.png Tested with Safari Technology Preview 233 21624.1.3 Firefox Nightly 147.0a1 14725.12.3 Google Chrome Canary 145.0.7569.0 7569.0 2164334 3 karlcow 2025-12-08 20:52:20 -0800 Need to dive in the code https://searchfox.org/wubkat/rev/904d209b92e989c17e5133a96c75eb75d2941d5a/Source/WebKit/UIProcess/WebPageProxy.cpp#11010-11055 2164358 4 karlcow 2025-12-09 00:34:55 -0800 Oh no the bug is here. https://searchfox.org/wubkat/rev/904d209b92e989c17e5133a96c75eb75d2941d5a/Source/WebCore/platform/graphics/cg/ImageUtilitiesCG.cpp#100-114 ``` if (!allowedMIMETypes.contains(WebCore::MIMETypeRegistry::mimeTypeForPath(path))) { needsTranscoding = true; return path; } ``` ["image/*", "image/heic"].contains("image/png"), it will add it to the list of files which needs to be transcoded. 2164359 5 karlcow 2025-12-09 00:36:26 -0800 "image/*" is treated as a literal string, not a wildcard. 2164364 6 webkit-bug-importer 2025-12-09 00:48:57 -0800 <rdar://problem/166124206> 2164365 7 karlcow 2025-12-09 00:52:34 -0800 Pull request: https://github.com/WebKit/WebKit/pull/55090 2170285 8 ews-feeder 2026-01-08 07:45:37 -0800 Committed 305283@main (4a46daaf002f): <https://commits.webkit.org/305283@main> Reviewed commits have been landed. Closing PR #55090 and removing active labels.