To provide more specific context, are you seeing this file name in , on a website's source code , or within a shared cloud folder ? Video preview (transcoded mp4) in the thumbnails folder

Expected behaviour. We can transcode uploaded movies to smaller size and the correct format and save it in the thumbnails folder ( Nextcloud pdf and video preview - Cloudron Forum

These files are usually created asynchronously using tools like ffmpeg to ensure the user can see a low-bandwidth version of the video without loading the entire original file.

The name "rendered_preview" followed by a number (like 6 ) often indicates a specific version or iteration in a sequence of generated assets within a software's internal file system.

If you are seeing this filename in a specific article or technical log, it likely points to a rather than a primary content file intended for direct download.

Systems like Nextcloud and ownCloud often convert original high-resolution uploads into smaller, web-compatible MP4 files stored in a "thumbnails" or "previews" folder.