best porn blocking tools for iPhone & Mac

Content & Privacy Restrictions in Screen Time are made for the purpose. Among other things, you have the option of managing which web pages your children can visit - you can, for example, block adult content. Screen Time can be found in Settings on your iPhone, and on your Mac.

Guidelines and Info here:

Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support

Of course, Apple already provides excellent tools for such purposes. If you were looking for something more, LULU by Objective See, is a phenomenal, open source, application where a user can create a custom list of domains, where ALL communications with such domains would be blocked. Publicly available lists of domains to block can be found online, which might or might not be regularly updated. This app is, however, only available for the Apple desktop OSs---at the moment.

I don't work for Objective See, but I would like to support this organization since I am able to use this incredible app for free. Aside from many included Apple system apps, the is one of the most valuable apps I have. From the research I have done, the app and organization are highly regarded. Perform your own due diligence, of course.