Open the Facebook app
Tap the menu icon
Scroll down and tap Settings & privacy
Tap Settings
Tap Browser or Media and Contacts, depending on your device
Tap Clear browsing data or Clear cache if available
Confirm the action
On Android:
Open Settings on your phone
Tap Apps
Tap Facebook
Tap Storage
Tap Clear cache
On iPhone:
Open Settings on your phone
Tap General
Tap iPhone Storage
Tap Facebook
Tap Offload App or Delete App
Reinstall Facebook from the App Store
Log out and log back in if needed