PunyCode Domain Detection por Francesco De Stefano

Is that really paypal.com? Phishing sites register names that look exactly like well-known ones by using letters from other alphabets: аpple.com with a Cyrillic “а”, раураӏ.com written entirely in Cyrillic, mozılla.com with a dotless “ı”. In the address bar they look identical. This add-on checks every address you open and stops the fakes.

Version 1.0 — rewritten from scratch, now also on Firefox for Android.

Stopped before it loads
- The address is checked before the request leaves your browser, so a fake site is caught even if it does not answer, and before it can run any code.
- A full-page warning stays until you decide: go to the real site in one click, go back, or open it anyway (once, or always for that site).

Shows you the trick
- The look-alike letters are highlighted, with their Unicode code, their alphabet and the Latin letter they imitate.
- You see the real address (the "xn--" Punycode form) and the name of the site being imitated.

Few false alarms
- Legitimate international names such as münchen.de, пример.рф or 中国.中国 are not treated as phishing: the toolbar icon just turns amber.
- A page is stopped when its name mixes alphabets (for example Latin and Cyrillic), is written only with letters that look Latin, or imitates one of 222 sites that phishing targets most (banks, payments, mail, shops, social networks) or a site you added.
- Also catches tricks with ordinary characters against those sites: paypa1.com, g00gle.com, rnicrosoft.com.
- Based on the Unicode security data (UTS #39, 1,797 look-alike characters).

More
- Toolbar icon: blue = plain address, amber = international address, red = possible imitation.
- Panel: verdict for the current page, "trust this site", and a box to check any link before opening it.
- Three modes: stop imitations (default), stop every international address, or icon only.
- Your own sites to protect (your bank, your company) and your trusted sites.
- Light and dark themes; designed for touch screens on Android.

Private: everything is checked on your device. The add-on makes no network requests and collects nothing.

Documentation and changelog: https://punycode-detection.sourceforge.io/
Free and open source (MIT) — https://sourceforge.net/projects/punycode-detection/