External drives · Media libraries and starting up from a drive
How do I move my TV app movies and shows to an external drive?
Short answer: In TV → Settings → Files, change the media folder to a folder on your external drive, then use File → Library → Organize Library to consolidate existing media there. Keep the drive connected when you use the TV app.
The TV app lets you choose where its media lives. Open TV → Settings → Files, click Change next to the media folder location, and pick a folder on your external drive. Then use File → Library → Organize Library and choose to consolidate files to copy existing media there. Check everything plays before deleting the old copies.
The drive must be connected whenever you open the TV app, or the media can't be found. Purchased movies and shows can also simply be deleted from the Mac and streamed or downloaded again later. See removing downloaded movies and shows.