Short answer: delete WhatsApp videos in two places. First clean chat media inside WhatsApp, then check Photos for saved copies. Many people remove the chat copy and miss the version that was already saved to the camera roll.
This is why WhatsApp video cleanup feels oddly incomplete. The app itself can hold heavy videos inside conversations, but iPhone Photos can also hold the same clips again. If both places are cluttered, deleting from only one side produces a smaller storage win than expected.
What to do first
Open WhatsApp and review Manage Storage or the heaviest chats first.
Delete large or old videos from the conversations that no longer matter.
Open Photos and review Recents or Videos for the saved copies of those clips.
Empty Recently Deleted if you need the storage back immediately.
Where the duplicates usually come from
Auto-save to Photos or manual saves from chats.
Forwarded videos that were downloaded more than once.
Edited or exported copies saved outside WhatsApp.
When an app is faster
An app is faster once the chat cleanup is done and the remaining problem is the saved media spread across the photo library. Cleanor for iPhone helps when WhatsApp videos turn into the same cleanup problem as other duplicate or large videos in Photos.
What people usually ask next
Does deleting a WhatsApp video from Photos remove it from the chat? No. Chat media and the saved camera-roll copy are separate.
Should I start in WhatsApp or Photos? Start in WhatsApp if the app itself is huge, then finish in Photos for saved copies.
What if the library still feels full afterwards? The next pass is usually other large videos, screenshots, or duplicate photos.
If the broader problem is still inside chats, read How to clean up WhatsApp storage on iPhone. If it is now a library problem, continue to How to delete large videos on iPhone.
WhatsApp video cleanup only feels complete when you clear both the chat media and the saved copies in Photos.