HEIC/HEIF MIME Type Mapping Is Inaccurate

[modi2918]

The MIME type map acknowledges that HEIC, HEIF, HEICS, and HEIFS files are not reliably distinguished by extension:

TODO: Needs improvement. All images with the following mime types seem to
have .heic file extension.
'heic' => 'image/heic',
'heif' => 'image/heif',
'heics' => 'image/heic-sequence',
'heifs' => 'image/heif-sequence',

Additionally, in the validation code, image/heif, image/heic-sequence, and image/heif-sequence files all get their extension normalized to .heic, which is inaccurate for sequence files and HEIF files that use different container types. This can cause upload validation failures and incorrect file extension assignment.

## Summary

Fixes inaccurate HEIC/HEIF MIME type mappings. Previously, all HEIF-family uploads (.heif, .heics, .heifs) were incorrectly mapped to and renamed as .heic because the $mime_to_ext array collapsed all variants into the heic extension.

Additionally, this PR fixes two related issues:

1. .heics and .heifs were missing from the wp_ext2type() image array, causing them not to be recognized as images in the Media Library.
2. Sub-size generation skipped non-image/heic HEIF variants because of a hardcoded mime type check.

## Changes

### src/wp-includes/functions.php

• Updated the $mime_to_ext array in wp_check_filetype_and_ext() to map each HEIF MIME type to its proper, distinct extension:
  • image/heif → heif
  • image/heic-sequence → heics
  • image/heif-sequence → heifs
• Added 'heic' to the $heic_images_extensions trigger array.
• Added 'heics' and 'heifs' to the image types array in wp_get_ext_types().
• Removed outdated comments indicating all HEIC/HEIF formats commonly use .heic.

### src/wp-admin/includes/image.php

• Replaced the explicit 'image/heic' === $mime_type check in wp_generate_attachment_metadata() with a call to wp_is_heic_image_mime_type(). This ensures all HEIF variants (not just image/heic) correctly trigger sub-size generation.

## Testing

Test	Result
Upload .heic file	✅ Remains .heic, sub-sizes generated correctly
Upload .heif file	✅ Remains .heif, sub-sizes generated correctly

Trac ticket: https://core.trac.wordpress.org/ticket/65297

## Use of AI Tools

AI assistance: No

[jorbin]

wp_is_heic_image_mime_type was added in 6.7. See [59315]. Setting the component to media since #62272 used that and wp_is_heic_image_mime_type is more of a general media function than upload specific.

[adamsilverstein]

Hi @modi2918 - thanks for the ticket and bug report.

If possible can you provide:

• A sample image of each type that you want to add support for. This would be helpful for adding tests.
• Any details about how you created these images or where they are commonly created - eg. how would WordPress users have them and be trying to upload them?

Hi @NoumaanAhamed - Thanks for the PR!

If possible can you provide:

A sample image of each type that you want to add support for. This would be helpful for adding tests.
Any details about how you created these images or where they are commonly created - eg. how would WordPress users have them and be trying to upload them?

Hi @NoumaanAhamed​[[Image(chrome-extension://hgomfjikakokcbkjlfgodhklifiplmpg/images/wp-logo.png)]] - Thanks for the PR!

If possible can you provide:

A sample image of each type that you want to add support for. This would be helpful for adding tests. Any details about how you created these images or where they are commonly created - eg. how would WordPress users have them and be trying to upload them?

The doc block the PR removes even mentions this - is it not accurate?

[modi2918]

### Where These File Types Come From in Everyday Use

test-heic.heic — Photos from iPhones

This is by far the most common HEIC file users upload. Apple introduced HEIC as the default photo format with iOS 11, and every iPhone since the iPhone 7 captures photos in this format unless the user changes the camera settings. A typical scenario is someone taking a photo on their iPhone, transferring it to a Mac, and then uploading it to a website or WordPress. These files usually use the heic major brand.

test-heif.heif — Photos from Android Devices

Many Android phones, including Samsung Galaxy and Google Pixel devices, support the HEIF format. Unlike Apple, Android devices generally use the mif1 major brand, which follows the MPEG HEIF specification. Files exported through Samsung Gallery, Google Photos, or other HEIF-compatible applications commonly use this format. This distinction is important because a file may have a .heif extension while still using the mif1 brand rather than heif, causing some file detection methods to miss it and rely on fallback detection mechanisms.

test-heics.heics — Apple Live Photos

Apple Live Photos combine a still image with a short motion clip. When exported, they can be stored as HEVC image sequences using the hevc major brand and typically carry the .heics extension. While less common than standard HEIC photos, users who back up or export their iPhone photo libraries may encounter these files.

test-heifs.heifs — Burst Photos and Image Sequences

Some Android devices and image-processing tools generate HEIF image sequences rather than single images. For example, burst-mode photos may be packaged using the msf1 major brand and saved with a .heifs extension. These files can also be produced by professional imaging software and tools that support the HEIF format, such as applications built on libheif.

Good catch, I've reverted those specific changes. @adamsilverstein

Attached sample files for testing. ( They all should resolve to .heic when uploaded )

​heic-files.zip

[adamsilverstein]

Thanks for adding the test image and an explanation of image sources. I’ll take a look!