node/doc/api/punycode.md

# punycode

    Stability: 2 - Stable

[Punycode.js][] is bundled with Node.js v0.5.1+. Use `require('punycode')` to
access it. (To use it with other Node.js versions, use npm to install the
`punycode` module first.)

## punycode.decode(string)
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added: v0.5.1
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Converts a Punycode string of ASCII-only symbols to a string of Unicode symbols.

```js
// decode domain name parts
punycode.decode('maana-pta'); // 'mañana'
punycode.decode('--dqo34k'); // '☃-⌘'
```

## punycode.encode(string)
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added: v0.5.1
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Converts a string of Unicode symbols to a Punycode string of ASCII-only symbols.

```js
// encode domain name parts
punycode.encode('mañana'); // 'maana-pta'
punycode.encode('☃-⌘'); // '--dqo34k'
```

## punycode.toASCII(domain)
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added: v0.6.1
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Converts a Unicode string representing a domain name to Punycode. Only the
non-ASCII parts of the domain name will be converted, i.e. it doesn't matter if
you call it with a domain that's already in ASCII.

```js
// encode domain names
punycode.toASCII('mañana.com'); // 'xn--maana-pta.com'
punycode.toASCII('☃-⌘.com'); // 'xn----dqo34k.com'
```

## punycode.toUnicode(domain)
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added: v0.6.1
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Converts a Punycode string representing a domain name to Unicode. Only the
Punycoded parts of the domain name will be converted, i.e. it doesn't matter if
you call it on a string that has already been converted to Unicode.

```js
// decode domain names
punycode.toUnicode('xn--maana-pta.com'); // 'mañana.com'
punycode.toUnicode('xn----dqo34k.com'); // '☃-⌘.com'
```

## punycode.ucs2
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### punycode.ucs2.decode(string)
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Creates an array containing the numeric code point values of each Unicode
symbol in the string. While [JavaScript uses UCS-2 internally][], this function
will convert a pair of surrogate halves (each of which UCS-2 exposes as
separate characters) into a single code point, matching UTF-16.

```js
punycode.ucs2.decode('abc'); // [0x61, 0x62, 0x63]
// surrogate pair for U+1D306 tetragram for centre:
punycode.ucs2.decode('\uD834\uDF06'); // [0x1D306]
```

### punycode.ucs2.encode(codePoints)
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Creates a string based on an array of numeric code point values.

```js
punycode.ucs2.encode([0x61, 0x62, 0x63]); // 'abc'
punycode.ucs2.encode([0x1D306]); // '\uD834\uDF06'
```

## punycode.version
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added: v0.6.1
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A string representing the current Punycode.js version number.

[Punycode.js]: https://mths.be/punycode
[JavaScript uses UCS-2 internally]: https://mathiasbynens.be/notes/javascript-encoding