Client Side Media iteration for WordPress 7.2 and beyond #80159

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1. adamsilverstein

   added

   [Type] EnhancementA suggestion for improvement.A suggestion for improvement.

   [Type] IterationScoped iteration of an effort from a tracking issue or overview issue ideally for a major release.Scoped iteration of an effort from a tracking issue or overview issue ideally for a major release.

   [Feature] Client Side MediaMedia processing in the browser with WASMMedia processing in the browser with WASM

   on Jul 13, 2026
2. adamsilverstein

   added sub-issues on Jul 13, 2026

   • Document-Isolation-Policy header scope is too narrow, breaking cross-window communication across admin screens #77633
   • Video transcoding to web-safe formats #79363
   • Local poster generation during video upload #79366
   • Resume uploads after a crash or reload (durable upload queue) #79365
   • Optimize previously uploaded media #79364
3. swissspidy

   added a sub-issue on Jul 15, 2026

   • Add support for live photo / burst mode (aka HEIC/HEIF image sequence) #79642
4. adamsilverstein

   added sub-issues on Jul 20, 2026

   • Notices don't span the full width of the editor when there are notes being rendered. #73917
   • Client-side media processing: add an opt-in filter to generate animated GIF sub-sizes #80383
5. adamsilverstein

   added the

   Task

   issue type on Jul 23, 2026
6. adamsilverstein

   added a sub-issue on Jul 24, 2026

   • Show progress when converting animated GIFs to video #80325
7. adamsilverstein

   added a sub-issue on Aug 12, 2026

   • HEIC upload hangs indefinitely instead of falling back to server-side processing #81043
8. t-hamano

   added this to WordPress 7.2 Editor Taskson Aug 13, 2026
9. 10 remaining items

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10. adamsilverstein

    added sub-issues on Aug 25, 2026

    • Media: make the uploader queue extensible #82035
    • Add a before/after comparison with a quality slider when optimizing media #82036
11. adamsilverstein commented on Aug 25, 2026

    

    adamsilverstein

    on Aug 25, 2026

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    I was going through open issues in https://github.com/swissspidy/media-experiments and there might be some relevant items in there for this iteration.

    Thanks for the links @swissspidy - I created some additional bug and enhancement issues based on those and linked back to your repo as reference material.

    👍React with 👍1Reacted by Pascal Birchler
12. adamsilverstein

    added sub-issues on Sep 4, 2026

    • Media: Dropping multiple files on a single-file placeholder sticks the upload snackbar, or ignores the limit #82041
    • Media upload: track upload progress with a per-session batch record instead of cumulative counters #82264
    • Notes: improve discoverability of feature #82349
    • Client-side media: process image edits (crop, rotate, flip) with wasm-vips instead of the server /edit endpoint #82358
    • Uploads from the editor's media library modal still go through the server #82409
13. gregbenz commented on Sep 7, 2026

    

    gregbenz

    on Sep 7, 2026

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    The planned upload and editing work looks like a strong foundation for broader HDR JPEG support. Could we define end-to-end acceptance criteria for JPEG gain-map preservation, identifying which workflows are covered in 7.2 and which need follow-up?

    The main questions I have are: Does HDR processing work across Gutenberg, Media Library, media modals, and third-party editors such as Elementor? What (if any) integration will third-party editors need to implement?

    Some of this already has implementation and tests underway. The goal would be to connect that work and make remaining coverage and limitations explicit, rather than assume everything must ship in 7.2. Would a dedicated HDR workflow/acceptance issue linked here be useful?
14. adamsilverstein

    added a sub-issue on Sep 8, 2026

    • Improve architecture of client-side media upload finalize #82613
15. adamsilverstein

    removed sub-issues on Sep 23, 2026

    • Notes: improve discoverability of feature #82349
    • Notices don't span the full width of the editor when there are notes being rendered. #73917
16. adamsilverstein

    added a sub-issue on Sep 25, 2026

    • Upload Media: Endless sideload loop when the browser can't decode a JPEG that wasm-vips can #83512
17. adamsilverstein commented on Sep 30, 2026

    

    adamsilverstein

    on Sep 30, 2026

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    Client Side Media Update: September 30, 2026

    Claude helped me pull this together from the sub-issues and their PRs; the priorities are mine:

    Summary

    Client-side media processing shipped in WordPress 7.1 for the block editor, and the 7.2 cycle has been about two things: bringing the same pipeline to the rest of the admin (the Media Library grid, Media > Add New, and the editor's media modal), and hardening the package based on what real uploads turned up once 7.1 was in the wild. WordPress 7.2 Beta 1 lands October 20-22, so there are about three weeks left to get the remaining 7.2 items reviewed and merged.

    The headline outside of the code is the progress on the Document-Isolation-Policy (DIP) standard. DIP is what lets WordPress enable SharedArrayBuffer for wasm-vips without breaking third-party embeds, and it has been Chromium-only so far. Since WordPress adopted it, Mozilla's position moved to positive, and on September 26 WebKit confirmed their portability concerns are resolved, leaving venue (upstreaming into HTML and Fetch) as the only remaining objection. To help move that along, WICG/document-isolation-policy#8 asks for the upstreaming work to start, WebKit bug 325516 formally requests an implementation, and DIP has been proposed for Interop 2027. Chrome shipped DIP on desktop in 137 and on Android in 146. This is WordPress helping move the web platform forward, and it is the path to client-side media in Firefox and Safari without a separate plugin.

    Top priorities before Beta 1

    These two are the "Top Tickets for 7.2" from the description, and both could use reviewer attention now:

    • Media Library uploads (Core): Enable client-side media uploads in the Media Library  wordpress-develop#12585 brings client-side processing to the upload grid and Media > Add New (Trac #65661). It has been through several review rounds with @westonruter (ES modules, TypeScript checking of the new admin scripts, a jQuery-free init hook for media-new.php), and the September 25 comment has screencasts of every format uploading against a trunk baseline. All review threads are resolved; it needs a final look and a commit.
    • Editor media modal (Gutenberg): Media: Handle editor's media modal uploads with client-side pipeline #82473 routes uploads from the classic media modal inside the block editor through the client-side pipeline (closing Uploads from the editor's media library modal still go through the server #82409, where HEIC uploads in the modal were still failing on hosts without HEIC support). @andrewserong tested it on September 28 and confirmed the sideload requests flow correctly, with two open scope questions about overriding the global wp.Uploader and the dependency on the upload-media store being present. Those need answers and probably a narrower hook before it merges.

    Highlights since the 7.1 wrap-up

    • Crossorigin injection removed under DIP: testing showed that under isolate-and-credentialless the crossorigin="anonymous" output buffer was unnecessary and actively broke media served from CDNs without CORS headers, and the buffer was also the source of a class of white-screen reports (Trac #65930, #65673). Media: Stop injecting crossorigin attributes under Document-Isolation-Policy #82614 merged September 11; the Core companion Media: Stop injecting crossorigin attributes under Document-Isolation-Policy wordpress-develop#13446 is open.
    • HEIC detection from the file header: Media: Detect HEIC uploads from the file header rather than the file name #81737 (merged September 22) detects HEIC from the file's own bytes rather than the extension or browser-reported MIME type, and bounds the ImageDecoder call with a timeout, closing HEIC upload hangs indefinitely instead of falling back to server-side processing #81043 (uploads hanging indefinitely) and Uploading an heic file with the wrong file extention doesn't fail or work properly #81707 (HEIC saved with a .jpg extension). Thanks to @singhakanshu00 for the earlier attempt in fix: Fixes HEIC uploads hanging indefinitely when ImageDecoder stalls #81211 that this superseded.
    • 7.1 Image block Resolution bug: Image block hides Resolution because media REST response contains empty media_details.sizes in WordPress 7.1 #81844 turned out to be the editor refetching the attachment before finalize had written media_details.sizes. Editor: Store the finalize response as the attachment record #81947 stores the finalize response as the attachment record, and the Core side (wpd #13412, r63564) prepares that response from the current post row. Both went out in 7.1.1 via Cherry-pick PRs for WP 7.1.1 #82383. Follow-up architecture notes from @andrewserong's review are captured in Improve architecture of client-side media upload finalize #82613.
    • Honest upload feedback: Media: Stop claiming "Upload complete" when every upload failed #81397 stops claiming "Upload complete" when every file failed (When uploading an OpenEXR image, first you are told it is uploaded and then you are told you can't upload that filetype #81708), Media: Report server upload failures in plain language #81735 reports server failures in plain language (Server errors misreported in client-side media upload. #81711), Media: Only blame the browser's codecs when HEIC really cannot be decoded #82265 only blames the browser's codecs when HEIC truly cannot be decoded, and Media: Reword the HEIC upload error and keep it up until dismissed #81130 rewords the HEIC error and keeps it up until dismissed.
    • Extensible upload queue: Pascal's suggestion in Media: make the uploader queue extensible #82035 turned into Upload Media: Rebuild the upload queue on an operation registry #82474, which rebuilds the existing queue on an operation registry before exposing anything public, followed by a stack of drafts: Upload Media: Public API for registering upload operations #83331 (public registration API) and three test plugins that prove it out, Upload Media: Dominant color test plugin as a consumer of the operation API #83332 (dominant color), Upload Media: Smallest encoding test plugin replaces a core operation #83333 (replace a core operation with a smallest-encoding step) and Upload Media: Video poster test plugin runs a step after the upload #83334 (video poster after upload). Upload media: guard processItem against re-entrant dispatch #83031 (re-entrancy guard on processItem) was split out of that review and is already merged. Thanks @swissspidy!
    • Client-side image edits: Client-side media: Process image edits (crop, rotate, flip) with wasm-vips #82362 runs the media editor's crop, rotate and flip through wasm-vips instead of the server /edit endpoint, so HDR gain maps survive edits (Client-side media: process image edits (crop, rotate, flip) with wasm-vips instead of the server /edit endpoint #82358, Cropping / mirroring image strips gain maps from HDR JPG #82295). @gregbenz confirmed in Playground that crop, flip and rotate stay HDR at every size. Core companion for the parent_image lineage: REST API: Record the source attachment of an uploaded image edit. wordpress-develop#13372 (Trac #66027).
    • Smart cropping explored and closed: Media: Use libvips smart crop to position hard-cropped image sizes when confidence is high #81706 and Media: Position hard crops around a detected subject, with a confidence gate #82049 looked at libvips attention cropping and subject-aware crops with a confidence gate. The results were not reliable enough to ship, and the best detector had a licensing problem in its WASM build, so this moves to plugin territory for now.

    Merged Gutenberg PRs since the last update

    Bug fixes and hardening

    • Media: Detect HEIC uploads from the file header rather than the file name #81737 Media: Detect HEIC uploads from the file header rather than the file name.
    • Editor: Store the finalize response as the attachment record #81947 Editor: Store the finalize response as the attachment record.
    • Media: Stop claiming "Upload complete" when every upload failed #81397 Media: Stop claiming "Upload complete" when every upload failed.
    • Media: Report server upload failures in plain language #81735 Media: Report server upload failures in plain language.
    • Media: Only blame the browser's codecs when HEIC really cannot be decoded #82265 Media: Only blame the browser's codecs when HEIC really cannot be decoded.
    • Media: Reword the HEIC upload error and keep it up until dismissed #81130 Media: Reword the HEIC upload error and keep it up until dismissed.
    • Media: Refuse a multi-file drop on a placeholder that takes one file #82046 Media: Refuse a multi-file drop on a placeholder that takes one file (Media: Dropping multiple files on a single-file placeholder sticks the upload snackbar, or ignores the limit #82041).
    • Media: keep indexed PNG sub-sizes indexed #81884 Media: keep indexed PNG sub-sizes indexed.
    • Media: Cover client-side big image scaling and orphaned files #81061 Media: Cover client-side big image scaling and orphaned files.
    • Upload Media: Fail the item when the /finalize request fails #80725 Upload Media: Fail the item when the /finalize request fails (@ramonjd).
    • Upload media: guard processItem against re-entrant dispatch #83031 Upload media: guard processItem against re-entrant dispatch (@swissspidy).
    • Media Utils: Preserve arrays in multipart form data #82353 Media Utils: Preserve arrays in multipart form data (@antwonw), fixing grouped image_size values.
    • Media: Remove the redundant __heicUploadSupport flag #80452 Media: Remove the redundant __heicUploadSupport flag.

    Cross-origin isolation

    • Media: Stop injecting crossorigin attributes under Document-Isolation-Policy #82614 Media: Stop injecting crossorigin attributes under Document-Isolation-Policy.
    • Media: Stop forcing crossorigin on IMG tags in media templates #80532 Media: Stop forcing crossorigin on IMG tags in media templates.
    • Docs: Fix broken link to the Document-Isolation-Policy explainer. #81790 Docs: Fix broken link to the Document-Isolation-Policy explainer (@jorgefilipecosta).

    Animated GIF and video

    • Video block: Remove GIF variation handling #82696 Video block: Remove GIF variation handling in favor of checking media_details.animated_video (@imraan011, Video block Gif variation has no way to pause the video #81943).
    • Video: Hide settings for the GIF variation #81142 Video: Hide settings for the GIF variation (@yogeshbhutkar).
    • Clarify the GIF Video variation description #81181 Clarify the GIF Video variation description.
    • Video, Cover: Don't autoplay in the editor when reduced motion is preferred #83337 and Cover: Don't autoplay embedded background videos when reduced motion is preferred #83452 Video, Cover: Don't autoplay in the editor when reduced motion is preferred (@im3dabasia, Video and Cover blocks: don't autoplay media when the visitor prefers reduced motion #82497).

    7.1.x backports

    • [7.1 Backport] -- Fix upload snackbar double-counting a single HEIC upload in Safari #80436, [7.1 Backport] -- Media: Add timeout and size guardrails to client-side GIF to video conversion #80420, [7.1 Backport] -- Worker threads: reject pending RPC calls on worker failure or termination  #80421, [7.1/Backport] Media: Remove the redundant __heicUploadSupport flag (#80452) #80486 (7.1 backports of the Safari HEIC double count, GIF guardrails, worker RPC rejection, and the HEIC flag removal).
    • Cherry-pick PRs for WP 7.1.1 #82383 Cherry-picks for 7.1.1, including Editor: Store the finalize response as the attachment record #81947, Media: Only blame the browser's codecs when HEIC really cannot be decoded #82265, Media: Refuse a multi-file drop on a placeholder that takes one file #82046, Media: Stop claiming "Upload complete" when every upload failed #81397 and Media: keep indexed PNG sub-sizes indexed #81884 (thanks @draganescu).

    Core (wordpress-develop) since the last update

    Committed:

    • wpd #12550 Media REST API: Fix sideload and finalize for EXIF rotated images, r62805 ↔ Media REST API: Fix sideload and finalize for EXIF rotated images #80295 (@andrewserong)
    • wpd #12508 REST API: Expose image_strip_meta and image_max_bit_depth in the index, r62806 ↔ Client Side Media: Honor image_strip_meta and image_max_bit_depth on the client upload path #80218
    • wpd #12598 Media: Fix animated GIF to video conversion failing due to a missing import map entry, r62807
    • wpd #12615 Media: Exclude IMG from crossorigin injection in media templates, r62819 (@itzmekhokan)
    • wpd #12689 Media: Skip server-side scaling during client-side media processing, r63014 (@itzmekhokan)
    • wpd #12825 REST API: Bound the size of media sideloaded from a URL, r63015 ↔ Media REST API: Backport sideload from url path upload size check #80659
    • wpd #12833 REST API: Always register the media creation arguments, r63018
    • wpd #13012 REST API: Bind finalize sub-size file names to their sideload, r63200
    • wpd #13412 REST API: Prepare the attachment finalize response from the current post row, r63564 (7.1.1) ↔ Editor: Store the finalize response as the attachment record #81947

    Open, pairing with Gutenberg work:

    • wpd #12585 Enable client-side media uploads in the Media Library (top priority, see above)
    • wpd #13446 Media: Stop injecting crossorigin attributes under Document-Isolation-Policy ↔ Media: Stop injecting crossorigin attributes under Document-Isolation-Policy #82614 (merged)
    • wpd #12846 REST API: Insert URL sideloads through the shared attachment path (approved by @andrewserong) ↔ External image sideload skips parts of the REST attachment creation path #82034
    • wpd #12572 Media: Add an opt-in filter to generate animated image sub-sizes ↔ Add an opt-in filter to generate animated image sub-sizes #80385
    • wpd #13372 REST API: Record the source attachment of an uploaded image edit ↔ Client-side media: Process image edits (crop, rotate, flip) with wasm-vips #82362
    • wpd #13323 Media: Sideload and clean up the web-safe companion of a transcoded video upload ↔ Client-side media: Add video transcoding to web-safe formats #79375
    • wpd #12352 Media: Preserve the .heif extension for genuine HEIF uploads
    • wpd #11298 Media: Broaden the Document-Isolation-Policy header to all admin pages (draft, approved by @swissspidy) ↔ Broaden DIP header scope to all admin pages #76662
    • wpd #13042 Media: Allow HEIC/HEIF sequence uploads when the server lacks editor support (draft) ↔ Client-side media: convert HEIC/HEIF image sequences (Live Photo / burst) to video #79647
    • wpd #12006 Media: Add JPEG XL upload support (draft) ↔ Add JPEG XL support #77584

    In flight and needing review

    Ready or close to ready for 7.2, in rough priority order:

    • Media: Handle editor's media modal uploads with client-side pipeline #82473 Media: Handle editor's media modal uploads with client-side pipeline. Needs answers to @andrewserong's scope questions, then a second review.
    • Fix endless sideload loop when the browser can't decode a big image #83530 Fix endless sideload loop when the browser can't decode a big image (@theaminulai). Fixes Upload Media: Endless sideload loop when the browser can't decode a JPEG that wasm-vips can #83512, found while recording the Media Library demos: a JPEG that wasm-vips decodes but createImageBitmap() rejects re-ran thumbnail generation forever and saturated the server with duplicate sideloads. This one affects 7.1 sites today, so it is a candidate for a 7.1.x backport once it lands. Needs a trunk merge for the changelog check and a review.
    • Add an opt-in filter to generate animated image sub-sizes #80385 Add an opt-in filter to generate animated image sub-sizes (Client-side media processing: add an opt-in filter to generate animated GIF sub-sizes #80383). Approved by @swissspidy, manually verified September 18 with a small test plugin (https://gist.github.com/adamsilverstein/16c35549d26024dd7266630fbd801442); needs a trunk merge for the new changelog validation and then it can go in, together with wpd No way to assign a custom post type to a category. 'show_in_rest' is enabled. #12572.
    • Media: Preserve EXIF metadata when converting HEIC to JPEG client-side #82040 Media: Preserve EXIF metadata when converting HEIC to JPEG client-side (Media: EXIF and IPTC metadata is lost when HEIC images are converted by client-side media #82033). Reworked to copy EXIF via vips after @andrewserong's review; his follow-up question about the Safari VideoDecoder path still needs an answer.
    • Client-side media: Process image edits (crop, rotate, flip) with wasm-vips #82362 Client-side media: Process image edits (crop, rotate, flip) with wasm-vips (Client-side media: process image edits (crop, rotate, flip) with wasm-vips instead of the server /edit endpoint #82358). Several rounds with @ramonjd addressed (memory guard before fetching the original, wp_edited_image_metadata firing for lineage); needs a final review.

    Nice to have for 7.2 if reviews line up:

    • Client-side media: Generate a local poster during video upload #79406 Client-side media: Generate a local poster during video upload (Local poster generation during video upload #79366).
    • Client-side media: convert HEIC/HEIF image sequences (Live Photo / burst) to video #79647 Client-side media: convert HEIC/HEIF image sequences (Live Photo / burst) to video (Add support for live photo / burst mode (aka HEIC/HEIF image sequence) #79642).
    • Upload Media: Rebuild the upload queue on an operation registry #82474 Upload Media: Rebuild the upload queue on an operation registry (@swissspidy), plus the stacked Upload Media: Public API for registering upload operations #83331, Upload Media: Dominant color test plugin as a consumer of the operation API #83332, Upload Media: Smallest encoding test plugin replaces a core operation #83333 and Upload Media: Video poster test plugin runs a step after the upload #83334. The registry itself has been tested across formats and sizes with no regressions; the public API is the part that wants design review.
    • Optimize existing media: compare before and after, with a quality slider #83411 Optimize existing media: compare before and after, with a quality slider (Add a before/after comparison with a quality slider when optimizing media #82036), stacked on Client Side Media: Optimize previously uploaded media #79509.

    Tracking for 7.3 or later:

    • Client-side media: Add video transcoding to web-safe formats #79375 Video transcoding to web-safe formats (Video transcoding to web-safe formats #79363). @andrewserong raised fair concerns about long videos and the cost of transcoding client-side; the current thinking is to scope it like HEIC (detect a format browsers cannot play and convert only then), with a size and duration guardrail.
    • Client Side Media: Optimize previously uploaded media #79509 Optimize previously uploaded media (Optimize previously uploaded media #79364).
    • Durable upload queue - resume uploads after reload/crash #79389 Durable upload queue, resume after reload or crash (Resume uploads after a crash or reload (durable upload queue) #79365).
    • Add JPEG XL support #77584 JPEG XL support (Add JPEG XL (JXL) support #76981), still gated on browser support.
    • Broaden DIP header scope to all admin pages #76662 Broaden the DIP header scope to all admin pages (Document-Isolation-Policy header scope is too narrow, breaking cross-window communication across admin screens #77633). Less urgent now that the Media Library work sets up isolation on its own screens.
    • Core Data: Discard entity record responses superseded by a newer request #81846 and Core Data: Cache-bust refetches of an already received resolution #81938 (core-data: discard superseded entity responses, cache-bust refetches), follow-ups from the Image block hides Resolution because media REST response contains empty media_details.sizes in WordPress 7.1 #81844 investigation.

    Open issues without a PR yet: #82034 (external image sideload skips part of the REST attachment path; @sanketio reports the first four items are implemented with tests and ready to open), #82613 (finalize architecture, discussion ongoing with @andrewserong and @swissspidy), #82264 (per-session batch record for upload progress), and #79559 (HDR NCLX/CICP color metadata in AVIF output, blocked upstream in libvips).

    Open questions

    • @gregbenz asked above for end-to-end acceptance criteria for HDR gain-map preservation across the editor, Media Library, media modals and third-party editors. With Client-side media: Process image edits (crop, rotate, flip) with wasm-vips #82362 and the Media Library work both in flight, a dedicated HDR workflow issue linked from here seems like the right way to make the coverage and limitations explicit. Greg, would you be up for opening that, using your Playground testing as the starting point?
    • Should Fix endless sideload loop when the browser can't decode a big image #83530 ship in a 7.1.x release once merged, given the loop can bog down a server? Input from the 7.1 release squad welcome.

    As always, testing and review help is appreciated, especially on wpd #12585 and #82473 before Beta 1. ?

    ❤️React with ❤️4Reacted by Ramon, Khokan Sardar, Andrew Serong and annezazu
18. josephfusco commented on Oct 14, 2026

    

    josephfusco

    on Oct 14, 2026

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    A request for the 7.3 list: measure audio waveform peaks in the browser at upload and store them in attachment metadata, so the Playlist block, the Audio block and plugins stop downloading and decoding the whole file to draw a waveform. Written up in #84712, with #83086 as the fallback for tracks without an attachment and #82035 as the likely seam.

    👍React with 👍1Reacted by Pascal Birchler