If you found this file on your device and want to know what it is without opening it, you can check the File Metadata :
Look at the or File Path . This will often tell you which app created the file (e.g., .../com.apple.Photos/ or .../WhatsApp/Media/ ).
the file (or long-press on mobile) and select Properties or Get Info .
Many apps (like TikTok, Instagram, or Telegram) rename video files using these long strings of letters and numbers when saving them to your phone's storage.