Windows uses file associations to decide which application opens a file type. A playlist opening in an editor or another player may be an association issue rather than a damaged playlist. You can choose an appropriate app without changing the file’s contents or account details.
Use open-with for a narrow test
Try the operating system’s open-with action and select a trusted compatible player. This tests the file without necessarily changing the default for every playlist. Confirm that the selected application supports local playlist imports rather than assuming any video app does.
Do not confuse files and links
A downloaded M3U file and a web address ending in .m3u can follow different opening paths. A browser may download the file instead of handing it to a desktop app. Use the player’s supported file or network-open command when the browser behaviour is unclear.
Keep private contents in mind
Opening the playlist in a text editor can reveal account-bearing media URLs. That can be useful for private inspection, but do not screen-share or upload the file casually. Changing the default app does not make those secrets less sensitive.
