GeezerVison

• Enter one domain name per line. Type Unicode on the left or Punycode on the right.
• Use a bare hostname to obtain readable Unicode; full URLs retain encoded hostnames and paths. Use the URL encoder for percent-encoded text.
• Conversion uses nontransitional Unicode UTS #46 processing: for example, faß.de becomes xn--fa-hia.de.

Punycode encodes Unicode text as ASCII; IDNA uses that algorithm for valid Unicode labels in internationalized domain names (IDN). IDNA adds the xn-- prefix to the encoded label, giving you the ASCII form used in domain registration, DNS records, TLS certificates and email configuration. Keep the distinction between encoding and identity in mind: a name built from similar-looking characters in different scripts can still be used in an IDN homograph attack.

Lookalike letters, including Cyrillic and Latin characters, let an IDN homograph attack disguise one domain as another. For internationalized domain names, a browser chooses whether to display Unicode characters or the ASCII form built with Punycode, so a suspicious name can look different between browsers. Check the underlying domain before signing in; a password manager with domain-based matching can help catch a mismatch that is hard to see.

An internationalized domain name (IDN) can contain non-ASCII characters from scripts such as Arabic, Chinese and Cyrillic, subject to IDNA and registry rules. IDNA uses Punycode to form ASCII labels with an xn-- prefix for DNS lookups; browsers apply separate rules to how they display those names. ICANN counted 151 IDN top-level domains across 23 scripts in June 2025, but the letters still deserve scrutiny — lookalikes can be used in homograph attacks.