IDNA (UTS 46) for JavaScript

This module is a IDNA UTS46 library for javascript. This is a maintained fork of the idna-uts46 library originally written by jcranmer.

The JS Punycode converter library is a great tool for handling Unicode domain names, but it only implements the Punycode encoding of domain labels, not the full IDNA algorithm. In simple cases, a mere conversion to lowercase text before input would seem sufficient, but the real mapping for strings is far more complex. This library implements the full mapping for these strings, as defined by UTS #46.

Requirements

Having Node.js >= 14.x set up and running, if you plan running it on webserver-side. We suggest using nvm.

Usage Instructions

NodeJS

    npm i idna-uts46-hx@latest --save

FYI: The default format of the plugin is ESM!

import { convert, toAscii, toUnicode } from 'idna-uts46-hx';
console.dir(convert(fußball.com));
console.dir(convert(fußball.de));
console.dir(convert([fußball.de, fußball.com]));
// ...

import * as uts46 from 'idna-uts46-hx';
console.dir(uts46.convert(fußball.com));
console.dir(uts46.convert(fußball.de));
console.dir(uts46.convert([fußball.de, fußball.com]));
// ...

Using it in-browser

Installation

You can rely on the github raw files

NOTE: The above is linking to master which is updating with each release and could come with breaking changes. Feel free to replace master in the urls with the tag/version of choice e.g. v5.0.5.

… or installing it also via npm and using the files from node_modules folder:

CJS: node_modules/idna-uts46-hx/dist/index.bundle.js
ESM: node_modules/idna-uts46-hx/dist/index.mjs

You can copy those files just over for using them as static files under /public in your project.

HTML / IFEE

NOTE: you have to define the path for attribute src accordingly!

<script src="index.bundle.js">
    const uts46 = idnaUts46;
    console.dir(uts46.convert(fußball.com));
    console.dir(uts46.convert(fußball.de));
    console.dir(uts46.convert([fußball.de, fußball.com]));
</script>

HTML / ESM

NOTE: you have to define the path for from accordingly!

<script type="module">
    import * as uts46 from "idna-uts46-hx/dist/index.mjs"
    console.dir(uts46.convert(fußball.com));
    console.dir(uts46.convert(fußball.de));
    console.dir(uts46.convert([fußball.de, fußball.com]));
</script>

Usage Examples

We provide only documentation and examples for the latest release.

IDNA mess for dummies

Unfortunately, the situation of internationalized domain names is rather complicated by the existence of multiple incompatible standards (IDNA2003 and IDNA2008, predominantly). While UTS #46 tries to bridge the incompatibility, there are four characters which cannot be so bridged: ß (the German sharp s), ς (Greek final sigma), and the ZWJ and ZWNJ characters. These are handled differently depending on the mode; in transitional mode, these strings are mapped to different ones, preserving capability with IDNA2003; in nontransitional mode, these strings are mapped to themselves, in accordance with IDNA2008.

Presently, this library uses transitional mode, compatible with all known browser implementations at this point. It is expected that, in the future, this will be changed to nontransitional mode.

It is highly recommended that you use the ASCII form of the label for storing or comparing strings.

API

uts46.toAscii

uts46.toAscii(domain, options={transitional: false, useStd3ASCII: false, verifyDnsLength: false })

Converts a domain name to the correct ASCII label. The second parameter is an optional options parameter, which has two configurable options. The transitional option controls whether or not transitional processing (see the IDNA mess for dummies section for more details) is requested, defaulting to false. The useStd3ASCII option controls whether or not characters that are illegal in domain names per the DNS specification should be omitted. The verifyDnsLength option controls whether or not the resulting DNS label should be checked for length validity (i.e., no empty components and not too long). The options parameter and its associated fields are all optional and should be omitted for most users.

/* eslint-disable */
uts46.toAscii('öbb.at') // 'xn-bb-eka.at'
uts46.toAscii('ÖBB.AT') // 'xn-bb-eka.at'
uts46.toAscii('XN-BB-EKA.AT') // 'xn-bb-eka.at'
uts46.toAscii('faß.de') // 'fass.de'
uts46.toAscii('faß.de', { transitional: true }) // 'fass.de'
uts46.toAscii('faß.de', { transitional: false }) // 'xn--fa-hia.de'
uts46.toAscii('xn--fa-hia.de', { transitional: false }) // 'xn--fa-hia.de'
uts46.toAscii(String.fromCodePoint(0xd0000)) // Error (as it is unassigned)

uts46.toUnicode

uts46.toUnicode(domain, options={useStd3ASCII: false})

Converts a domain name to a normalized Unicode label. The second parameter is an optional options parameter. The useStd3ASCII option controls whether or not characters that are illegal in domain names per the DNS specification should be omitted. The latter parameter is optional and should be omitted for most users.

/* eslint-disable */
uts46.toUnicode('xn-bb-eka.at') // 'öbb.at'
uts46.toUnicode('ÖBB.AT') // 'öbb.at'
uts46.toUnicode('O\u0308BB.AT') // 'öbb.at'
uts46.toUnicode('faß.de') // 'faß.de'
uts46.toUnicode('xn--fa-hia.de') // 'faß.de'
uts46.toUnicode('﷼') // "ریال"
uts46.toUnicode(String.fromCodePoint(0xd0000)) // Error (as it is unassigned)

uts46.convert

uts46.convert(domain)

Converts a domain name in correct way. Returning IDNA2003 / IDNA2008 strings where it makes sense as this is dependent on the domain extension / TLD.

/* eslint-disable */
uts46.convert('xn-bb-eka.at') // { IDN: 'öbb.at', PC: 'xn-bb-eka.at' }
uts46.convert(['öbb.at', 'xn--fa-hia.de']) // { IDN: ['öbb.at', 'faß.de'], PC: ['xn-bb-eka.at', 'xn--fa-hia.de'] }

Known issues

It also does not try to implement the Bidi and contextual rules for validation: these do not affect any mapping of the domain names; instead, they restrict the set of valid domain names. Since registrars shouldn’t be accepting these names in the first place, a domain that violates these rules will simply fail to resolve.