TinyMCE in classic editor does not support modern video formats

[blackstar1991]

WP does not support webp, avi formats for the classic editor. Can someone help and make them uwaliable like in Block Templates ?

[nabilaminhridoy]

Hi there 👋

I’ve tested this issue on the latest WordPress 6.8.3 with the Classic Editor plugin (v1.6.3) and can confirm that the problem still exists.

When trying to insert .webp or .avi files via the “Add Media” modal in TinyMCE, the files are not recognized or previewed correctly.
Meanwhile, the Block Editor supports .webp uploads and displays them as expected.

This seems to be related to the allowed MIME types or TinyMCE’s media plugin configuration in the Classic Editor integration.

Steps to reproduce:

1. Activate the Classic Editor plugin.
2. Go to “Posts → Add New”.
3. Click “Add Media” and try uploading a .webp or .avi file.
4. The file is rejected or not displayed in the editor.

Expected:
The Classic Editor should handle .webp and modern video formats similar to the Block Editor.

If needed, I can help test or submit a patch for this.

@nabilaminhridoy

[lakshyajeet]

Reproduction Report

Description

This report validates whether the issue can be reproduced. The testing confirms that while .webm files now appear to function in the Classic Editor, .avi files remain unsupported for playback. However, the .avi failure is likely a browser-level limitation rather than a WordPress bug, as .avi is not a standard format for the HTML5 <video> tag across modern browsers.

Environment

• WordPress: 7.1-alpha-62161-src
• PHP: 8.3.30
• Server: nginx/1.29.7
• Database: mysqli (Server: 8.4.8 / Client: mysqlnd 8.3.30)
• Browser: Chrome 146.0.0.0
• OS: macOS
• Theme: Twenty Twenty-Five 1.4
• MU Plugins: None activated
• Plugins:
  • Classic Editor 1.6.7

Actual Results

1. ✅ Partial Reproduction: While .webm files successfully upload and play back in both editors, .avi files fail to render a preview or play back in both the Block Editor and Classic Editor.
2. ❌ Observation: The .avi playback issue appears to be a browser compatibility constraint. Most modern browsers do not support the AVI container within the native <video> element, leading to the reported "unsupported" behavior regardless of the editor used.

Additional Notes

• WebM: During testing, .webm files worked as expected in the Classic Editor, suggesting that recent updates may have already addressed the MIME type registration for this specific format.
• AVI: Since the Block Editor also fails to play .avi files, this is not a TinyMCE-specific issue but a general limitation of web-standard video playback. WordPress successfully handles the file upload, but the browser cannot render the stream.

[lakshyajeet]

Issue reproduction in Block Editor.

[lakshyajeet]

Issue reproduction in Classic Editor.

[blackstar1991]

It would probably be worth prohibiting the uploading of .avi files into the body of documents if they cannot be played.

​https://developer.mozilla.org/en-US/docs/Web/Media/Guides/Formats/Video_codecs
​https://caniuse.com/?search=video+format

[sukhendu2002]

Reproduction Report

Environment

• WordPress: 7.2-alpha-63166-src
• Subdirectory: No
• PHP: 8.3.33
• Server: nginx/1.31.3
• Database: mysqli (Server: 8.4.11 / Client: mysqlnd 8.3.33)
• Browser: Chrome 151.0.0.0
• OS: macOS
• Theme: Twenty Twenty-Five 1.5
• MU Plugins: None activated
• Plugins:
  • Classic Editor 1.7.0
  • Test Reports 1.3.1

Steps taken

1. Activated Classic Editor and opened a new post.
2. Uploaded and inserted a WebM video using Add Media.
3. Confirmed that its player appeared and the video played.
4. Uploaded and inserted an AVI video.
5. Confirmed that AVI was inserted as a link rather than a video player.
6. In the Block Editor, WebM played but AVI was unsupported by Chrome.

❌ Bug is not occurring

Expected behavior

• The ticket reports that WebM does not preview or play in Classic Editor. It worked correctly during testing.
• AVI is not supported by Chrome, so Classic Editor correctly inserts it as a link.

Additional Notes

• The description says .webp, but comments refer to .webm; this test used WebM.
• Preventing AVI selection in the Block Editor would be a separate enhancement.

Screenshots/Screencast with results

WebM playing in Classic Editor.

AVI inserted as a link.

AVI has no embed option

[blackstar1991]

@sukhendu2002

AVI inserted as a link.

Why is this file type even available as an option in this element? *The output isn't what I expected.