18521mp4 -

: Ensure your Direct Message settings are set to allow messages from "Everyone" or "Friends" in your Privacy settings.

: Standard text messages typically limit video files to 3.5 MB . 18521mp4

: Open your messaging app, select the recipient, and tap the + or attachment icon to select your video from your gallery. : Ensure your Direct Message settings are set

If "18521.mp4" is a video you want to share with someone via text/DM on TikTok: select the recipient

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: