Sometimes internet service providers (ISPs) have filters directly over their network which customers can opt-in to, while in some countries ISP filters are mandatory for Government censorship. But in Western countries, filters are usually an extra product or service an individual household, organisation, school or library chooses to put on their internet connection independently.
Typically filters use automated algorithms to classify sites into categories based on their content. But no filter is foolproof and they inevitably allow access to sites they are meant to block, while over-blocking some sites by mistake. They may compensate for this by allowing users to report wrongly-blocked sites and suggest how sites should be classified and blocked.
When you consider the range of content on the internet, it’s easy to understand the appeal of filters if you have children or underage users to cater for. Despite their flaws, their broad appeal is that they provide some control over the content on a family’s or organisation’s internet connection. Provided filters are not controlled by the government and used to suppress dissent, as happens in authoritarian countries, or forced onto the public under a false pretext and operated without transparency, as has happened in UK, then there is nothing wrong with individuals or organisations choosing to put filters over their own connections, is there?