Punycode converter (IDN converter)

How to use the Punycode converter?

• Place multiple items on multiple lines
• If you enter a whole URL (must properly begin with a protocol name, e.g. http://), the domain name will be Punycode encoded/decoded, the path will be URL encoded or decoded
• The tool uses the IDNA2008 standard, but with Unicode TR#46 Compatibility Processing. Therefore, some conflicting characters are encoded using the old IDNA2003 standard

What is Punycode?

Punycode is an encoding that converts Unicode characters into the limited ASCII subset that DNS can handle, making internationalized domain names (IDN) possible. Every Punycode-encoded domain label starts with the xn-- prefix. You'll run into Punycode when registering IDN domains, configuring DNS records, requesting SSL certificates, or setting up email on non-ASCII domains. The same mechanism that enables multilingual domains also enables IDN homograph attacks, where attackers register lookalike domains using visually identical characters from different scripts.

What is an IDN homograph attack?

An IDN homograph attack exploits the visual similarity between characters from different scripts -- like Cyrillic and Latin -- to register domains that look identical to legitimate ones. The attack is made possible by internationalized domain names and the way browsers decode Punycode for display. A password manager is one of the best passive defenses, since it matches on the actual domain string rather than what you see on screen.

What is IDN?

An Internationalized Domain Name (IDN) is a domain name that uses characters beyond ASCII -- Arabic, Chinese, Cyrillic, or any other Unicode script. Browsers silently convert IDN domains to Punycode (with an xn-- prefix) so the DNS can resolve them. As of 2025, 151 IDN top-level domains exist across 23 scripts, though homograph attacks remain a security concern.