Editor: PHP backports for Client Side Media by adamsilverstein · Pull Request #10868 · WordPress/wordpress-develop

adamsilverstein · 2026-02-04T22:44:59Z

This PR contains the PHP backports for the client-side media processing feature, enabling the editor to perform client-side image resizing, thumbnail generation, and format conversion using WebAssembly.

Preloaded Settings

The following site settings are now preloaded in both the post editor and site editor:

image_sizes - Available image size configurations
image_size_threshold - Big image size threshold (default 2560px)
image_output_formats - Output format mappings for image conversion
jpeg_interlaced - Whether to use progressive/interlaced JPEG encoding
png_interlaced - Whether to use interlaced PNG encoding
gif_interlaced - Whether to use interlaced GIF encoding

REST API: Index Endpoint

Added media processing settings to the REST API index (/wp-json/wp/v2/):

image_sizes - All registered image sizes with dimensions and crop settings
image_size_threshold - Big image size threshold
image_output_formats - Format conversion mappings

REST API: Attachments Endpoint

New Fields

filename - Original attachment file name
filesize - File size in bytes
exif_orientation - EXIF orientation value (1-8) for client-side rotation handling

New Parameters

generate_sub_sizes - When false, disables server-side sub-size generation and EXIF rotation
convert_format - When false, disables automatic image format conversion

New Sideload Endpoint

Added /wp/v2/media/{id}/sideload endpoint for uploading sub-sized images to an existing attachment. Used by client-side media processing to upload generated image sizes without creating new attachments. Supports both images and PDFs.

PDF Improvements

Improved missing_image_sizes field handling for PDFs, which use the fallback_intermediate_image_sizes filter instead of wp_get_missing_image_subsizes().

Cross-Origin Isolation

Added COOP (Cross-Origin-Opener-Policy) and COEP (Cross-Origin-Embedder-Policy) headers in the block editor to enable SharedArrayBuffer for WebAssembly-based processing. Includes:

Output buffer to automatically add crossorigin="anonymous" attributes to external resources
Media templates updated with crossorigin attributes for audio, img, and video tags

WASM Support

Added AddType directive for WebAssembly files to .htaccess rules, enabling serving .wasm files for client-side media processing libraries like wasm-vips.

Tests

Updated REST API tests for the new attachment fields and sideload endpoint.

Gutenberg PRs:

Gutenberg tracking issue: WordPress/gutenberg#75062

Trac ticket: https://core.trac.wordpress.org/ticket/62243

This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

github-actions · 2026-02-04T22:50:41Z

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Add filename and filesize REST fields to the attachments endpoint for client-side media processing. The filename returns the original attachment file name, and filesize returns the file size in bytes.

Add exif_orientation field to the attachments REST endpoint for client-side EXIF rotation handling. Values 1-8 follow the EXIF specification, where 1 means no rotation is needed.

Add generate_sub_sizes and convert_format parameters to the attachments POST endpoint for client-side media processing control. When generate_sub_sizes is false, server-side sub-size generation and EXIF rotation are disabled. When convert_format is false, automatic image format conversion is disabled.

Add sideload endpoint at /wp/v2/media/{id}/sideload for uploading sub-sized images to an existing attachment. Used by client-side media processing to upload generated image sizes without creating new attachments. Supports both images and PDFs.

Add PDF-specific handling for the missing_image_sizes field in the attachments endpoint. PDFs use fallback_intermediate_image_sizes filter to determine which thumbnail sizes should be generated, unlike regular images which use wp_get_missing_image_subsizes().

Add COOP and COEP headers in the block editor to enable SharedArrayBuffer for WebAssembly-based client-side media processing. Includes output buffer to automatically add crossorigin="anonymous" attributes to external resources.

Add AddType directive for WebAssembly files to the mod_rewrite_rules filter. This enables serving .wasm files for client-side media processing using libraries like wasm-vips.

Override wp_print_media_templates to add crossorigin="anonymous" attributes to audio, img, and video tags. Required for cross-origin isolation compliance in the media library modal.

Update test_get_item_schema to expect 32 properties instead of 29, adding assertions for the new filename, filesize, and exif_orientation fields. Add the sideload endpoint to expected routes in schema test. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

westonruter

Sorry for what may be an unsolicited early review, as the PR is still a draft.

src/wp-includes/rest-api/class-wp-rest-server.php

src/wp-includes/media.php

westonruter · 2026-02-08T01:15:30Z

src/wp-includes/media.php

+}
+
+/**
+ * Filters the list of rewrite rules formatted for output to an .htaccess file.


What about for Nginx?

With help from Claude:

Nginx's default mime.types file has included application/wasm since at least 2017 (see nginx/nginx@aef7dd8), so most Nginx servers already serve .wasm files with the correct MIME type out of the box.

The AddType directive here is a safety net for older Apache configurations that might not have it. WordPress has no mechanism to modify Nginx configuration (it only manages .htaccess).

That said, it might be worth adding a note in the dev notes that server administrators on Nginx (or other servers) with custom/stripped-down MIME type configurations should ensure application/wasm is present. Planning on a dev note already, so I'll make sure to add something on this. Also might be worth checking that the server fallback kicks in when wasm type isn't configured correctly on the server.

westonruter · 2026-02-08T01:16:13Z

src/wp-includes/media.php

+			foreach ( $tags as $tag ) {
+				$html = (string) str_replace( "<$tag", "<$tag crossorigin=\"anonymous\"", $html );
+			}


This should use the HTML Tag Processor too as it has been leveraged above.

Done in cbc0328

src/wp-includes/rest-api/class-wp-rest-server.php

adamsilverstein · 2026-02-12T06:17:27Z

Sorry for what may be an unsolicited early review, as the PR is still a draft.

No worries, happy to have your feedback. Indeed I started working on this pr before the Gutenberg work had merged to get ahead and be more prepared - so it may change a bit, but probably not much at this point.

Co-authored-by: Weston Ruter <westonruter@gmail.com>

Replace naive str_replace with WP_HTML_Tag_Processor for adding crossorigin attributes to media template tags. Since templates live inside <script type="text/html"> tags (raw text per the HTML spec), extract each script block's content and process it as a standalone HTML fragment.

EXIF orientation value 0 (undefined/no EXIF data) was being used as-is instead of falling through to the default of 1. Add a > 0 guard so orientation values of 0 or negative are treated as no rotation needed.

Add new media endpoint args (generate_sub_sizes, convert_format), sideload route, image size settings, and filename/filesize fields. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

westonruter · 2026-02-17T21:00:34Z

src/wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php

+	 *                       The arguments for `CREATABLE` requests are
+	 *                       checked for required values and may fall-back to a given default.
+	 *                       Default WP_REST_Server::CREATABLE.
+	 * @return array Endpoint arguments.


Suggested change

* @return array Endpoint arguments.

* @return array<string, array<string, mixed>> Endpoint arguments.

westonruter · 2026-02-17T21:01:24Z

src/wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php

+	 *                       Default WP_REST_Server::CREATABLE.
+	 * @return array Endpoint arguments.
+	 */
+	public function get_endpoint_args_for_item_schema( $method = WP_REST_Server::CREATABLE ) {


Suggested change

public function get_endpoint_args_for_item_schema( $method = WP_REST_Server::CREATABLE ) {

public function get_endpoint_args_for_item_schema( string $method = WP_REST_Server::CREATABLE ): array {

westonruter · 2026-02-17T21:02:18Z

src/wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php

+	 * @param int $attachment_id Attachment ID.
+	 * @return string|null Attachment file name, or null if not found.
+	 */
+	protected function get_attachment_filename( $attachment_id ) {


Suggested change

protected function get_attachment_filename( $attachment_id ) {

protected function get_attachment_filename( $attachment_id ): ?string {

westonruter · 2026-02-17T21:02:29Z

src/wp-includes/rest-api/endpoints/class-wp-rest-attachments-controller.php

+	 * @param int $attachment_id Attachment ID.
+	 * @return int|null Attachment file size in bytes, or null if not available.
+	 */
+	protected function get_attachment_filesize( $attachment_id ) {


Suggested change

protected function get_attachment_filesize( $attachment_id ) {

protected function get_attachment_filesize( $attachment_id ): ?int {

add preload patchs for client side media

3ddfba4

REST API: Add media processing settings to index endpoint

86938a4

adamsilverstein mentioned this pull request Feb 4, 2026

Create sub-sized images WordPress/gutenberg#74566

Merged

36 tasks

adamsilverstein added 8 commits February 4, 2026 15:28

REST API: Add filename and filesize fields to attachments

21c0229

Add filename and filesize REST fields to the attachments endpoint for client-side media processing. The filename returns the original attachment file name, and filesize returns the file size in bytes.

REST API: Add exif_orientation field to attachments

b912c2f

Add exif_orientation field to the attachments REST endpoint for client-side EXIF rotation handling. Values 1-8 follow the EXIF specification, where 1 means no rotation is needed.

Media: Add cross-origin isolation support

5356039

Add COOP and COEP headers in the block editor to enable SharedArrayBuffer for WebAssembly-based client-side media processing. Includes output buffer to automatically add crossorigin="anonymous" attributes to external resources.

Media: Add WASM MIME type to .htaccess rules

357c406

Add AddType directive for WebAssembly files to the mod_rewrite_rules filter. This enables serving .wasm files for client-side media processing using libraries like wasm-vips.

Media: Add crossorigin attributes to media templates

78abc16

Override wp_print_media_templates to add crossorigin="anonymous" attributes to audio, img, and video tags. Required for cross-origin isolation compliance in the media library modal.

adamsilverstein changed the title ~~Editor: Add REST API preloaded paths for client-side media processing~~ Editor: PHP back posrts for client-side media Feb 5, 2026

adamsilverstein changed the title ~~Editor: PHP back posrts for client-side media~~ Editor: PHP backports for client-side media Feb 5, 2026

adamsilverstein changed the title ~~Editor: PHP backports for client-side media~~ Editor: PHP backports for Client Side Media Feb 5, 2026

adamsilverstein added sync-gutenberg and removed sync-gutenberg labels Feb 5, 2026

adamsilverstein self-assigned this Feb 5, 2026

adamsilverstein and others added 2 commits February 4, 2026 22:10

Docs: Update @SInCE tags from 6.9.0 to 7.0.0

e847d8c

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

westonruter reviewed Feb 8, 2026

View reviewed changes

src/wp-includes/rest-api/class-wp-rest-server.php Outdated Show resolved Hide resolved

adamsilverstein and others added 7 commits February 13, 2026 22:10

Update src/wp-includes/media.php

59c91e3

Co-authored-by: Weston Ruter <westonruter@gmail.com>

Update src/wp-includes/media.php

6c7c7cd

Co-authored-by: Weston Ruter <westonruter@gmail.com>

Update src/wp-includes/media.php

4f33ce6

Co-authored-by: Weston Ruter <westonruter@gmail.com>

Update src/wp-includes/rest-api/class-wp-rest-server.php

54826e2

Co-authored-by: Weston Ruter <westonruter@gmail.com>

Fix EXIF orientation 0 treated as valid value

0a6c8ab

EXIF orientation value 0 (undefined/no EXIF data) was being used as-is instead of falling through to the default of 1. Add a > 0 guard so orientation values of 0 or negative are treated as no rotation needed.

Update REST API QUnit fixtures for Client Side Media changes

68db73d

Add new media endpoint args (generate_sub_sizes, convert_format), sideload route, image size settings, and filename/filesize fields. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

github-actions bot mentioned this pull request Feb 15, 2026

PHP backports for WP 7.0 WordPress/gutenberg#74043

Open

adamsilverstein mentioned this pull request Feb 16, 2026

Client Side Media iteration for WordPress 7.0 WordPress/gutenberg#74333

Open

westonruter reviewed Feb 17, 2026

View reviewed changes

	* @return array Endpoint arguments.
	* @return array<string, array<string, mixed>> Endpoint arguments.

	public function get_endpoint_args_for_item_schema( $method = WP_REST_Server::CREATABLE ) {
	public function get_endpoint_args_for_item_schema( string $method = WP_REST_Server::CREATABLE ): array {

	protected function get_attachment_filename( $attachment_id ) {
	protected function get_attachment_filename( $attachment_id ): ?string {

	protected function get_attachment_filesize( $attachment_id ) {
	protected function get_attachment_filesize( $attachment_id ): ?int {

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adamsilverstein commented Feb 4, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Preloaded Settings

REST API: Index Endpoint

REST API: Attachments Endpoint

New Fields

New Parameters

New Sideload Endpoint

PDF Improvements

Cross-Origin Isolation

WASM Support

Tests

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github-actions bot commented Feb 4, 2026

Test using WordPress Playground

Some things to be aware of

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adamsilverstein commented Feb 12, 2026

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adamsilverstein commented Feb 4, 2026 •

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