IDN Safe is a free Firefox extension designed to enhance user security by blocking internationalized domain names (IDNs), also known as punycode domains. These types of domains can be used to create deceptive website addresses that visually mimic legitimate sites, posing a risk of phishing attacks. The extension identifies these potentially harmful domains and prevents users from accidentally visiting them, thus safeguarding personal information and online security.

In addition to its blocking capabilities, IDN Safe allows users to manage their settings by temporarily permitting specific domains or whitelisting them entirely. By default, all IDNs are blocked, providing a proactive approach to online safety. This extension is a valuable tool for anyone looking to improve their browsing experience by reducing the risk of encountering fraudulent websites.