What is Punycode used for?

Punycode (RFC 3492) encodes internationalized domain names that contain non-ASCII characters into a limited ASCII form prefixed with xn--, so the existing DNS system can route them.

Does it convert whole domains?

Yes. Each dot-separated label is handled independently — Unicode labels gain the xn-- prefix when encoded, and xn-- labels are turned back into Unicode when decoded.

What does the xn-- prefix mean?

xn-- is the ACE (ASCII Compatible Encoding) prefix that marks a label as Punycode-encoded. Software sees the prefix and knows to decode the rest back into Unicode for display.

Why are internationalized domains encoded at all?

The DNS only handles a limited ASCII character set (letters, digits and hyphens). Punycode maps non-ASCII characters into that set so domains in any script can be stored and resolved by existing infrastructure.

Are ASCII-only labels changed?

No. A label with only standard ASCII characters needs no encoding and is left unchanged — only labels containing non-ASCII characters are converted to the xn-- form.

Why should I be cautious about Punycode domains?

Look-alike characters from other scripts can make a Punycode domain resemble a familiar brand (a homograph attack). Decoding a suspicious xn-- domain reveals the real characters behind it.

Is my domain sent anywhere?

No. The full Bootstring algorithm runs in your browser, so the domains you enter never leave your device.

Punycode Converter — Gera Tools

Punycode converter for internationalized domains

Punycode is the encoding from RFC 3492 that lets internationalized domain names (IDNs) — those with accents or non-Latin scripts — work with the ASCII-only DNS. This tool converts a Unicode domain into its xn-- ASCII form and decodes it back, useful for developers, registrars and anyone inspecting an unfamiliar xn-- domain.

How it works

The converter implements the full Bootstring algorithm and processes a domain one dot-separated label at a time:

encode: each label with non-ASCII chars → "xn--" + bootstring encoding
decode: each "xn--" label → original Unicode characters
plain ASCII labels are left unchanged

Handling labels separately is why a multi-part domain round-trips cleanly.

Example

Encoding münchen.de:

münchen (contains ü) → xn—mnchen-3ya
de is ASCII → unchanged
Result: xn—mnchen-3ya.de

Decoding the same value returns münchen.de.

Direction	Input	Output
Encode	münchen.de	xn—mnchen-3ya.de
Decode	xn—mnchen-3ya.de	münchen.de
Encode	example.com	example.com (unchanged)

Everything runs locally in your browser.