Use a parental control app like Google Family Link
Install a website blocker app from the Play Store
Set up DNS filtering using a service like NextDNS or OpenDNS
Use browser settings to block specific sites if the browser supports it
Add blocked websites to a hosts file on rooted devices
Use router-level website blocking for all devices on the network
Enable SafeSearch and restricted modes in apps and browsers
Use a firewall app to restrict internet access for specific apps
Block websites through a VPN with filtering features
Remove or limit access to browsers you do not want used