Chrome browser: .mkv Uploads are rejected: "Files of type 'video/matroska' are not allowed"

[samuelinniger]

Describe the bug
When selecting a .mkv video for upload via the Opencast plugin, an error occurs specifically in Google Chrome. The issue does not persist in Safari or Firefox, where the same files are accepted correctly.

(?) The issue could to be caused by a recent change in the Chromium engine regarding MIME type handling. According to RFC 9559, the MIME type video/x-matroska is deprecated in favor of video/matroska.

Screenshots

Environment (please complete the following information):

• ILIAS version: [v9.17 2026-01-20]
• Plugin version: [9.3.1]
• Opencast version: 17
• Browser: Chrome 146.0.7680.80

Additional context
https://issues.chromium.org/issues/40921769
https://www.rfc-editor.org/rfc/rfc9559#name-media-types

[chfsx]

Hi @samuelinniger
thanks for the report, this is most probably an Issue in ILIAS core and not in the plugin. I'll have a look at the fileupload in ILIAS and will open a mantis issue if it is a core issue.

[dagraf]

@chfsx: Do you have an update on this? Is this a core or a plugin issue?

[chfsx]

It can be changes in the Plugin by adding 'video/matroska' to the list of allowed mime-types, this is a trivial fix and I tested it locally, shall I push this directly without a PR and ReviewApp?

[dagraf]

Yes. Thx!