This is the best website blocker. totally suits my case where I wanted to allow only specific set of websites to use. Loved it's simplicity

This is the only extension I've found that allows both a whitelist and a blacklist to run at the same time. Really helpful. I just wish it was open source so I could help with some of the TODOs.

This should be password protected, One main reason of whitelisting something is to limit the site access for others using / sharing the computer, and if anyone could change whitelisted sites, then the purpose is lost.

The author fixed a bug where I did not see the icon on the toolbar. It blocked sites for me, but I am using it in conjunction with PublicFox to lock my settings from being changed. PublicFox will not lock this since the settings are accessible in the toolbar. So I ended up using Simple Blocker, which worked to enforce a whitelist for me.