[Bug]: App Store "Discover" freezes Safari: intro video is AV1 WebM + H.264 High 10 MP4, neither playable on Intel/M1/M2 Macs #65872

⚠️ This issue respects the following points: ⚠️

• This is not a troubleshooting question, general support matter, or webserver/proxy problem, but likely a bug (if unsure, ask the Community Help Forum).
• This issue is not already reported on Github OR solved at the Community Help Forum (I've searched!).
• I'm using a maintained major version of Nextcloud Server and tested against the latest patch level. (Supported major versions and current patch levels).
• I agree to follow Nextcloud's Code of Conduct.
• I've tried my best to provide clear reproduction steps that someone unfamiliar with this bug could use to reproduce it.

Bug description

Since the Discover feed started showing the Nextcloud Hub intro video (added in nextcloud/screenshots#55), opening Apps → Discover in Safari 27 freezes the whole tab: the sidebar stops responding and the rest of the page is never rendered. Chrome works.

The feed offers two sources:

{"src": ".../nextcloud-hub-intro.webm", "mime": "video/webm"},
{"src": ".../nextcloud-hub-intro.mp4",  "mime": "video/mp4"}

Neither of them is playable in Safari on Macs without an AV1 hardware decoder (Intel Macs, M1/M2):

• The WebM is AV1 (4K). canPlayType('video/webm') returns "maybe" (no codecs in the mime), but canPlayType('video/webm; codecs="av01.0.08M.08"') returns "".
• The MP4 is H.264 High 10 (10-bit, profile_idc 110, avc1.6E0033). canPlayType('video/mp4; codecs="avc1.6E0033"') returns "". Apple's hardware decoders don't support 10-bit H.264.

Safari then hangs on the unsupported AV1 stream instead of failing gracefully. The hang itself is a WebKit bug (reported to Apple separately), but the feed content triggers it.

I verified outside Nextcloud: the same two files in a plain <video><source> test page freeze Safari. A standard 8-bit H.264 video plays fine. On my instance I re-encoded the cached MP4 to 8-bit H.264 (ffmpeg -c:v libx264 -profile:v high -pix_fmt yuv420p) and put MP4 first, and the Discover page then works in Safari, video included.

Suggested fix:

1. Re-encode nextcloud-hub-intro.mp4 as 8-bit H.264 (High profile, yuv420p).
2. List the MP4 source first, or declare the WebM codec: "mime": "video/webm; codecs=\"av01.0.12M.08\"".

Steps to reproduce

1. Use Safari 27 on an Intel Mac (likely also M1/M2, which lack AV1 decoding too; not verified).
2. Log in as admin and open Apps → Discover.
3. The page freezes at the intro video card; nothing on the page responds anymore.

Expected behavior

The Discover page loads, and the intro video plays (or is skipped if unsupported) in Safari, as it does in Chrome.

Nextcloud Server version

35

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.4

Web server

Apache (supported)

Database engine version

PostgreSQL

Is this bug present after an update or on a fresh install?

Upgraded to a MAJOR version (ex. 31 to 32)

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

List of activated Apps

Nextcloud Signing status

Nextcloud Logs

Additional info

• Nextcloud 35.0.2, All-in-One (Docker) on Raspberry Pi (Debian 13, aarch64), PHP 8.4.27, PostgreSQL 18.6
• Browser: Safari 27.0 on macOS 15.8.1, MacBook Pro 2017 (Intel, no AV1 hardware decoding)
• Safari main thread is blocked in WebKit::AudioVideoRendererRemote::videoLayerSize() (captured with sample).
• Related: the MP4 is also served as application/octet-stream without HTTP Range support by /apps/appstore/api/v1/discover/media; Safari needs video/mp4 + 206 responses to play it.