Use built-in parental controls on your phone
On iPhone, enable Screen Time and set Content Restrictions
On Android, use Digital Wellbeing or Family Link
Install a website-blocking app from the app store
Add the websites you want to block to the app’s blacklist
Set a passcode so the block settings cannot be changed easily
Use DNS filtering services to block websites at the network level
Change browser settings to restrict access to certain sites
Block websites through your Wi-Fi router settings
Use SafeSearch and restricted mode in search apps and browsers
Remove or limit browsers that bypass restrictions
Keep restrictions enabled with a strong device passcode