Amazon Fire TV User Manual page 46

Component or Feature
Device Types
Size
File Format
Supported Media
46
Requirement
microSD cards
128GB or smaller
FAT32
Apps and Games
At this time, Amazon Video titles, Amazon Music
content, and photos stored in your Amazon Cloud
Drive cannot be saved to external storage. You can
stream your videos and music and access your
photos over your Fire TV's Internet connection.
Content saved to microSD storage can't be
transferred to other devices or microSD cards.