Open the Settings app on your iPhone
Tap General
Tap iPhone Storage
Find and tap WhatsApp
Tap Offload App to remove the app and keep its documents and data, or tap Delete App to remove the app and its data
Reinstall WhatsApp from the App Store if you deleted or offloaded it
Open WhatsApp and sign in again
In WhatsApp, go to Settings
Tap Storage and Data
Tap Manage Storage
Delete large files, media, or chats to reduce WhatsApp storage use
Go to individual chats and delete unwanted photos, videos, and documents
Turn off auto-download in WhatsApp Settings if you want to reduce future cache buildup