If you are trying to add text overlays to a video file for a post, you can do so through the built-in editors of most apps:
If "18521.mp4" is a video you want to share with someone via text/DM on TikTok: 18521mp4
: Many apps like TikTok offer an Auto-lyrics or Captions feature that automatically generates text from your video's audio. Sending a Video via Text Message If you are trying to add text overlays