Enables client-side media processing on Firefox and Safari via COEP/COOP cross-origin isolation headers, and adds HEIC/HEIF upload support with automatic client-side conversion to JPEG.

WordPress 7.0 and Gutenberg include client-side media processing powered by WebAssembly (wasm-vips). This requires cross-origin isolation, which is achieved via Document-Isolation-Policy (DIP) on Chrome 137+.

However, Firefox and Safari do not yet support DIP, so client-side media processing is disabled on those browsers.

This plugin restores support by sending the older COEP/COOP headers on browsers where DIP is not available:

• Sends Cross-Origin-Opener-Policy: same-origin and Cross-Origin-Embedder-Policy: credentialless (or require-corp on Safari) headers in the block editor.
• Adds crossorigin="anonymous" attributes to cross-origin resources.
• Adds credentialless attribute to iframes so they continue working under COEP.
• Filters embed previews for providers that do not support credentialless iframes (Facebook, SmugMug).

HEIC support was removed from WordPress core's wasm-vips build due to LGPL/GPL license incompatibility. This plugin re-enables HEIC upload support by converting images client-side:

• Enabled by default — can be toggled under Settings → Media.
• HEIC/HEIF images are automatically converted to JPEG in the browser before upload.
• Uses the heic2any library, loaded dynamically from an external CDN only when a HEIC file is detected.
• heic2any uses libheif (LGPL-3.0) for decoding. Since it is loaded at runtime from a CDN rather than bundled with the plugin, it is treated as a separate work and does not affect the plugin's GPL-2.0-or-later license.

• WordPress 6.8+ with the Gutenberg plugin, or WordPress 7.0+.
• The client-side media processing feature must be enabled.

1. Upload the client-side-media-experiments folder to /wp-content/plugins/.
2. Activate the plugin through the Plugins menu in WordPress.
3. The COEP/COOP headers activate automatically on browsers that need them. HEIC support is enabled by default.

add_filter( 'csme_use_coep_coop', '__return_false' );

Navigate to Settings → Media and uncheck HEIC Support, or programmatically:

update_option( 'csme_heic_enabled', 0 );

Use the csme_heic_library_url filter to point to your own hosted copy of heic2any:

add_filter( 'csme_heic_library_url', function () {
    return 'https://example.com/heic2any.min.js';
} );

This plugin is licensed under GPL-2.0-or-later.

The HEIC conversion library (heic2any / libheif) is LGPL-3.0 licensed and loaded at runtime from an external CDN as a separate work.