IDN Punycode Converter

DNS speaks ASCII only

The domain system accepts a restricted ASCII set, so a domain containing non-Latin characters is encoded into an ASCII form beginning xn--. München becomes xn--mnchen-3ya. The Unicode form is what a browser displays; the Punycode form is what is actually resolved and what appears in certificates and logs.

Homograph attacks exploit the gap

Cyrillic а, е and о are visually identical to their Latin counterparts. A domain using them renders as apple.com and resolves as something entirely different. Browsers defend by displaying the Punycode form when a label mixes scripts or uses a script inconsistent with the browser's locale, which is why a suspicious link sometimes appears as xn-- gibberish — that display is the warning, not a fault.

Encoding is per label

Each dot-separated label is converted independently, so only the labels containing non-ASCII get the xn-- prefix. A domain can mix encoded and plain labels, and a subdomain may be encoded while the parent is not.

Email addresses are a separate standard

Internationalised email uses SMTPUTF8 rather than Punycode for the local part, and support is inconsistent across providers. Punycode applies to the domain half; the part before the @ follows different rules and frequently fails silently.

Verifying a link

Converting a suspicious URL to Punycode reveals whether the visible characters are what they appear to be. A domain that looks entirely Latin but converts to an xn-- form contains non-Latin characters somewhere, which is decisive evidence.

Related tools

• User Agent Parser — Parse a User-Agent string into browser, engine, operating system and device. Explains why UA strings are unreliable and what to use instead.
• QR Code Generator — Generate QR codes for URLs, text, Wi-Fi and contact details. Adjustable error correction and size, produced entirely in your browser.
• Credit Card Validator — Validate a card number with the Luhn algorithm and identify the issuing network from its prefix. Runs locally, nothing is transmitted.
• Text Case Converter — Convert text between camelCase, PascalCase, snake_case, kebab-case, CONSTANT_CASE, Title Case and sentence case. Runs entirely in your browser.