Is your feature request related to a problem? Please describe.

Yes. Thumbnail generation may be disabled in the Local Filesystem plugin — either as it is the default or by admin choice (e.g., to avoid excessive file creation). When browsing a folder with larger images (e.g., 10 JPEGs at ~5 MB each), the thumbnails in the Media Manager view loads painfully slow, especially on slower network connections. It takes minutes.

Describe the solution you'd like

If permanent thumbnail generation is disabled, Joomla should still:

• Detect when an image exceeds a size threshold (e.g. 100 KB)
• Generate and serve a temporary, on-the-fly thumbnail to improve the frontend performance

This would greatly improve the user experience, while keeping the filesystem clean when desired.

Additional context

This feature request could be of minor priority as there is always the option to enable the creation of thumbnails.

• Tested with local installed Joomla 5.3.1-dev
• Browser: Firefox 127
• Network throttling: 1536 kbps / 40 ms latency (via Firefox Web Developer Tools menu)
• OS: macOS Sequoia 15.4
• 10 images: JPEG, each ~5 MB
• Thumbnail generation in Local Filesystem plugin: disabled