Some apps remove metadata from videos and photos and some do not, and most of them never say which. Discord says in its engineering blog that it strips EXIF from images; Apple and Google document how to share without location; WhatsApp, Telegram, Signal, Instagram, TikTok and Reddit publish nothing clear on what they remove. The behaviour also changes with how you send a file, the phone you send it from and the app’s current version.
So the honest answer to “does Discord remove metadata” or “does WhatsApp remove metadata” is: check the copy that arrives. This page sets out what each vendor actually states, marks what is only reported by users, and gives a simple test you can run on any app. It does not list test results of its own.
The test uses this site’s viewer, which reads files in your browser without uploading them. If you would rather not rely on any app, remove the metadata yourself before you send.