One of the less hyped features of iOS is the ability to filter sensitive content warnings.
Sensitive Content Warnings feature uses on-device machine learning to analyze & block photos and videos sent to you that might contain nudity.
To enable Sensitive Content Warning on iPhone, open the Settings app, go to Privacy & Security, and turn on the toggle beside Sensitive Content Warning.
After enabling the feature, photos or videos that appear to contain nudity will be automatically blurred and display a warning message.