The best tool a child has for screening materials on the internet is his or her brain. Teach children about exploitation, pornography, hate literature, excessive violence, and other issues that concern you, so they know how to respond when they see this material.
Choose a commercial online service that offers parental control features. These can block content that is not clearly marked as appropriate for children, including social media, chat rooms, bulletin board, news groups, and discussion groups. These tools also can block internet access entirely.
Purchase blocking software and design your own safety system. Filters for computers and smartphones can block sites by name, search for unacceptable words and block access to sites containing those words, block entire categories of material, and prevent children from giving out personal information.
Monitor your children when they're online -- including phone use -- and monitor the amount of time spent online. If a child becomes uneasy or defensive when you walk into a room or look over his or her shoulder, this could be a sign that something is up.