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index.html
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<!doctype html><html lang="en">
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
<title>User Locale Preferences</title>
<meta content="width=device-width, initial-scale=1, shrink-to-fit=no" name="viewport">
<link href="https://www.w3.org/StyleSheets/TR/2021/cg-draft" rel="stylesheet">
<meta content="Bikeshed version f043d3484, updated Fri Feb 17 10:53:48 2023 -0800" name="generator">
<link href="https://github.com/romulocintra/user-locale-client-hints" rel="canonical">
<meta content="bc89a6b0b2f7a5654cbdb96a3050c47d8f397a24" name="document-revision">
<style>/* style-autolinks */
.css.css, .property.property, .descriptor.descriptor {
color: var(--a-normal-text);
font-size: inherit;
font-family: inherit;
}
.css::before, .property::before, .descriptor::before {
content: "‘";
}
.css::after, .property::after, .descriptor::after {
content: "’";
}
.property, .descriptor {
/* Don't wrap property and descriptor names */
white-space: nowrap;
}
.type { /* CSS value <type> */
font-style: italic;
}
pre .property::before, pre .property::after {
content: "";
}
[data-link-type="property"]::before,
[data-link-type="propdesc"]::before,
[data-link-type="descriptor"]::before,
[data-link-type="value"]::before,
[data-link-type="function"]::before,
[data-link-type="at-rule"]::before,
[data-link-type="selector"]::before,
[data-link-type="maybe"]::before {
content: "‘";
}
[data-link-type="property"]::after,
[data-link-type="propdesc"]::after,
[data-link-type="descriptor"]::after,
[data-link-type="value"]::after,
[data-link-type="function"]::after,
[data-link-type="at-rule"]::after,
[data-link-type="selector"]::after,
[data-link-type="maybe"]::after {
content: "’";
}
[data-link-type].production::before,
[data-link-type].production::after,
.prod [data-link-type]::before,
.prod [data-link-type]::after {
content: "";
}
[data-link-type=element],
[data-link-type=element-attr] {
font-family: Menlo, Consolas, "DejaVu Sans Mono", monospace;
font-size: .9em;
}
[data-link-type=element]::before { content: "<" }
[data-link-type=element]::after { content: ">" }
[data-link-type=biblio] {
white-space: pre;
}
</style>
<style>/* style-colors */
/* Any --*-text not paired with a --*-bg is assumed to have a transparent bg */
:root {
color-scheme: light dark;
--text: black;
--bg: white;
--unofficial-watermark: url(https://www.w3.org/StyleSheets/TR/2016/logos/UD-watermark);
--logo-bg: #1a5e9a;
--logo-active-bg: #c00;
--logo-text: white;
--tocnav-normal-text: #707070;
--tocnav-normal-bg: var(--bg);
--tocnav-hover-text: var(--tocnav-normal-text);
--tocnav-hover-bg: #f8f8f8;
--tocnav-active-text: #c00;
--tocnav-active-bg: var(--tocnav-normal-bg);
--tocsidebar-text: var(--text);
--tocsidebar-bg: #f7f8f9;
--tocsidebar-shadow: rgba(0,0,0,.1);
--tocsidebar-heading-text: hsla(203,20%,40%,.7);
--toclink-text: var(--text);
--toclink-underline: #3980b5;
--toclink-visited-text: var(--toclink-text);
--toclink-visited-underline: #054572;
--heading-text: #005a9c;
--hr-text: var(--text);
--algo-border: #def;
--del-text: red;
--del-bg: transparent;
--ins-text: #080;
--ins-bg: transparent;
--a-normal-text: #034575;
--a-normal-underline: #bbb;
--a-visited-text: var(--a-normal-text);
--a-visited-underline: #707070;
--a-hover-bg: rgba(75%, 75%, 75%, .25);
--a-active-text: #c00;
--a-active-underline: #c00;
--blockquote-border: silver;
--blockquote-bg: transparent;
--blockquote-text: currentcolor;
--issue-border: #e05252;
--issue-bg: #fbe9e9;
--issue-text: var(--text);
--issueheading-text: #831616;
--example-border: #e0cb52;
--example-bg: #fcfaee;
--example-text: var(--text);
--exampleheading-text: #574b0f;
--note-border: #52e052;
--note-bg: #e9fbe9;
--note-text: var(--text);
--noteheading-text: hsl(120, 70%, 30%);
--notesummary-underline: silver;
--assertion-border: #aaa;
--assertion-bg: #eee;
--assertion-text: black;
--advisement-border: orange;
--advisement-bg: #fec;
--advisement-text: var(--text);
--advisementheading-text: #b35f00;
--warning-border: red;
--warning-bg: hsla(40,100%,50%,0.95);
--warning-text: var(--text);
--amendment-border: #330099;
--amendment-bg: #F5F0FF;
--amendment-text: var(--text);
--amendmentheading-text: #220066;
--def-border: #8ccbf2;
--def-bg: #def;
--def-text: var(--text);
--defrow-border: #bbd7e9;
--datacell-border: silver;
--indexinfo-text: #707070;
--indextable-hover-text: black;
--indextable-hover-bg: #f7f8f9;
--outdatedspec-bg: rgba(0, 0, 0, .5);
--outdatedspec-text: black;
--outdated-bg: maroon;
--outdated-text: white;
--outdated-shadow: red;
--editedrec-bg: darkorange;
}
</style>
<style>/* style-counters */
body {
counter-reset: example figure issue;
}
.issue {
counter-increment: issue;
}
.issue:not(.no-marker)::before {
content: "Issue " counter(issue);
}
.example {
counter-increment: example;
}
.example:not(.no-marker)::before {
content: "Example " counter(example);
}
.invalid.example:not(.no-marker)::before,
.illegal.example:not(.no-marker)::before {
content: "Invalid Example" counter(example);
}
figcaption {
counter-increment: figure;
}
figcaption:not(.no-marker)::before {
content: "Figure " counter(figure) " ";
}
</style>
<style>/* style-dfn-panel */
:root {
--dfnpanel-bg: #ddd;
--dfnpanel-text: var(--text);
}
.dfn-panel {
position: absolute;
z-index: 35;
width: 20em;
min-width: min-content;
max-width: 300px;
height: auto;
max-height: 500px;
overflow: auto;
padding: 0.5em 0.75em;
font: small Helvetica Neue, sans-serif, Droid Sans Fallback;
background: var(--dfnpanel-bg);
color: var(--dfnpanel-text);
border: outset 0.2em;
white-space: normal; /* in case it's moved into a pre */
}
.dfn-panel:not(.on) { display: none; }
.dfn-panel * { margin: 0; padding: 0; text-indent: 0; }
.dfn-panel > b { display: block; }
.dfn-panel a { color: var(--dfnpanel-text); }
.dfn-panel a:not(:hover) { text-decoration: none !important; border-bottom: none !important; }
.dfn-panel > b + b { margin-top: 0.25em; }
.dfn-panel ul { padding: 0; }
.dfn-panel li { list-style: inside; }
.dfn-panel.activated {
display: inline-block;
position: fixed;
left: .5em;
bottom: 2em;
margin: 0 auto;
max-width: calc(100vw - 1.5em - .4em - .5em);
max-height: 30vh;
}
.dfn-paneled { cursor: pointer; }
</style>
<style>/* style-issues */
a[href].issue-return {
float: right;
float: inline-end;
color: var(--issueheading-text);
font-weight: bold;
text-decoration: none;
}
</style>
<style>/* style-md-lists */
/* This is a weird hack for me not yet following the commonmark spec
regarding paragraph and lists. */
[data-md] > :first-child {
margin-top: 0;
}
[data-md] > :last-child {
margin-bottom: 0;
}
</style>
<style>/* style-selflinks */
:root {
--selflink-text: white;
--selflink-bg: gray;
--selflink-hover-text: black;
}
.heading, .issue, .note, .example, li, dt {
position: relative;
}
a.self-link {
position: absolute;
top: 0;
left: calc(-1 * (3.5rem - 26px));
width: calc(3.5rem - 26px);
height: 2em;
text-align: center;
border: none;
transition: opacity .2s;
opacity: .5;
}
a.self-link:hover {
opacity: 1;
}
.heading > a.self-link {
font-size: 83%;
}
.example > a.self-link,
.note > a.self-link,
.issue > a.self-link {
/* These blocks are overflow:auto, so positioning outside
doesn't work. */
left: auto;
right: 0;
}
li > a.self-link {
left: calc(-1 * (3.5rem - 26px) - 2em);
}
dfn > a.self-link {
top: auto;
left: auto;
opacity: 0;
width: 1.5em;
height: 1.5em;
background: var(--selflink-bg);
color: var(--selflink-text);
font-style: normal;
transition: opacity .2s, background-color .2s, color .2s;
}
dfn:hover > a.self-link {
opacity: 1;
}
dfn > a.self-link:hover {
color: var(--selflink-hover-text);
}
a.self-link::before { content: "¶"; }
.heading > a.self-link::before { content: "§"; }
dfn > a.self-link::before { content: "#"; }
</style>
<style>/* style-syntax-highlighting */
pre.idl.highlight {
background: var(--borderedblock-bg, var(--def-bg));
}
code.highlight { padding: .1em; border-radius: .3em; }
pre.highlight, pre > code.highlight { display: block; padding: 1em; margin: .5em 0; overflow: auto; border-radius: 0; }
.highlight:not(.idl) { background: rgba(0, 0, 0, .03); }
c-[a] { color: #990055 } /* Keyword.Declaration */
c-[b] { color: #990055 } /* Keyword.Type */
c-[c] { color: #708090 } /* Comment */
c-[d] { color: #708090 } /* Comment.Multiline */
c-[e] { color: #0077aa } /* Name.Attribute */
c-[f] { color: #669900 } /* Name.Tag */
c-[g] { color: #222222 } /* Name.Variable */
c-[k] { color: #990055 } /* Keyword */
c-[l] { color: #000000 } /* Literal */
c-[m] { color: #000000 } /* Literal.Number */
c-[n] { color: #0077aa } /* Name */
c-[o] { color: #999999 } /* Operator */
c-[p] { color: #999999 } /* Punctuation */
c-[s] { color: #a67f59 } /* Literal.String */
c-[t] { color: #a67f59 } /* Literal.String.Single */
c-[u] { color: #a67f59 } /* Literal.String.Double */
c-[cp] { color: #708090 } /* Comment.Preproc */
c-[c1] { color: #708090 } /* Comment.Single */
c-[cs] { color: #708090 } /* Comment.Special */
c-[kc] { color: #990055 } /* Keyword.Constant */
c-[kn] { color: #990055 } /* Keyword.Namespace */
c-[kp] { color: #990055 } /* Keyword.Pseudo */
c-[kr] { color: #990055 } /* Keyword.Reserved */
c-[ld] { color: #000000 } /* Literal.Date */
c-[nc] { color: #0077aa } /* Name.Class */
c-[no] { color: #0077aa } /* Name.Constant */
c-[nd] { color: #0077aa } /* Name.Decorator */
c-[ni] { color: #0077aa } /* Name.Entity */
c-[ne] { color: #0077aa } /* Name.Exception */
c-[nf] { color: #0077aa } /* Name.Function */
c-[nl] { color: #0077aa } /* Name.Label */
c-[nn] { color: #0077aa } /* Name.Namespace */
c-[py] { color: #0077aa } /* Name.Property */
c-[ow] { color: #999999 } /* Operator.Word */
c-[mb] { color: #000000 } /* Literal.Number.Bin */
c-[mf] { color: #000000 } /* Literal.Number.Float */
c-[mh] { color: #000000 } /* Literal.Number.Hex */
c-[mi] { color: #000000 } /* Literal.Number.Integer */
c-[mo] { color: #000000 } /* Literal.Number.Oct */
c-[sb] { color: #a67f59 } /* Literal.String.Backtick */
c-[sc] { color: #a67f59 } /* Literal.String.Char */
c-[sd] { color: #a67f59 } /* Literal.String.Doc */
c-[se] { color: #a67f59 } /* Literal.String.Escape */
c-[sh] { color: #a67f59 } /* Literal.String.Heredoc */
c-[si] { color: #a67f59 } /* Literal.String.Interpol */
c-[sx] { color: #a67f59 } /* Literal.String.Other */
c-[sr] { color: #a67f59 } /* Literal.String.Regex */
c-[ss] { color: #a67f59 } /* Literal.String.Symbol */
c-[vc] { color: #0077aa } /* Name.Variable.Class */
c-[vg] { color: #0077aa } /* Name.Variable.Global */
c-[vi] { color: #0077aa } /* Name.Variable.Instance */
c-[il] { color: #000000 } /* Literal.Number.Integer.Long */
</style>
<style>/* style-darkmode */
@media (prefers-color-scheme: dark) {
:root {
--text: #ddd;
--bg: black;
--unofficial-watermark: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='400' height='400'%3E%3Cg fill='%23100808' transform='translate(200 200) rotate(-45) translate(-200 -200)' stroke='%23100808' stroke-width='3'%3E%3Ctext x='50%25' y='220' style='font: bold 70px sans-serif; text-anchor: middle; letter-spacing: 6px;'%3EUNOFFICIAL%3C/text%3E%3Ctext x='50%25' y='305' style='font: bold 70px sans-serif; text-anchor: middle; letter-spacing: 6px;'%3EDRAFT%3C/text%3E%3C/g%3E%3C/svg%3E");
--logo-bg: #1a5e9a;
--logo-active-bg: #c00;
--logo-text: white;
--tocnav-normal-text: #999;
--tocnav-normal-bg: var(--bg);
--tocnav-hover-text: var(--tocnav-normal-text);
--tocnav-hover-bg: #080808;
--tocnav-active-text: #f44;
--tocnav-active-bg: var(--tocnav-normal-bg);
--tocsidebar-text: var(--text);
--tocsidebar-bg: #080808;
--tocsidebar-shadow: rgba(255,255,255,.1);
--tocsidebar-heading-text: hsla(203,20%,40%,.7);
--toclink-text: var(--text);
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<body class="h-entry">
<div class="head">
<p data-fill-with="logo"><a class="logo" href="https://www.w3.org/"> <img alt="W3C" height="48" src="https://www.w3.org/StyleSheets/TR/2021/logos/W3C" width="72"> </a> </p>
<h1 class="p-name no-ref" id="title">User Locale Preferences</h1>
<p id="w3c-state"><a href="https://www.w3.org/standards/types#CG-DRAFT">Draft Community Group Report</a>, <time class="dt-updated" datetime="2023-02-22">22 February 2023</time></p>
<div data-fill-with="spec-metadata">
<dl>
<dt>This version:
<dd><a class="u-url" href="https://github.com/romulocintra/user-locale-client-hints">https://github.com/romulocintra/user-locale-client-hints</a>
<dt>Issue Tracking:
<dd><a href="https://github.com/romulocintra/user-locale-client-hints/issues/">GitHub</a>
<dt class="editor">Editors:
<dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:[email protected]">Romulo Cintra</a> (<a class="p-org org" href="https://igalia.com">Igalia</a>)
<dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:[email protected]">Ujjwal Sharma</a> (<a class="p-org org" href="https://igalia.com">Igalia</a>)
<dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:[email protected]">Ben Allen</a> (<a class="p-org org" href="https://igalia.com">Igalia</a>)
<dt>Tests:
<dd>(<a href="https://github.com/w3c/web-platform-tests/labels/user-locale-client-hints">ongoing work</a>)
</dl>
</div>
<div data-fill-with="warning"></div>
<p class="copyright" data-fill-with="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2023 the Contributors to the User Locale Preferences Specification, published by the <a href="https://www.w3.org/community/wicg/">Web Platform Incubator Community Group</a> under the <a href="https://www.w3.org/community/about/agreements/cla/">W3C Community Contributor License Agreement (CLA)</a>.
A human-readable <a href="http://www.w3.org/community/about/agreements/cla-deed/">summary</a> is available. </p>
<hr title="Separator for header">
</div>
<div class="p-summary" data-fill-with="abstract">
<h2 class="no-num no-toc no-ref heading settled" id="abstract"><span class="content">Abstract</span></h2>
<p>This specification introduces a set of <code>Client Hints</code> headers and a homologous <code>Javascript API</code> that will allow a reliable way to access User Locale Preferences information from the Web Platform to help craft better user experiences. Allowing web developers to access this information will allow them to improve the accessibility and usability of their websites, and bring the user experience of web applications closer to that of native applications.</p>
</div>
<div data-fill-with="at-risk"></div>
<h2 class="no-num no-toc no-ref heading settled" id="status"><span class="content">Status of this document</span></h2>
<div data-fill-with="status">
<p> This specification was published by the <a href="https://www.w3.org/community/wicg/">Web Platform Incubator Community Group</a>.
It is not a W3C Standard nor is it on the W3C Standards Track.
Please note that under the <a href="https://www.w3.org/community/about/agreements/cla/">W3C Community Contributor License Agreement (CLA)</a> there is a limited opt-out and other conditions apply.
Learn more about <a href="http://www.w3.org/community/">W3C Community and Business Groups</a>. </p>
<p></p>
</div>
<div data-fill-with="at-risk"></div>
<nav data-fill-with="table-of-contents" id="toc">
<h2 class="no-num no-toc no-ref" id="contents">Table of Contents</h2>
<ol class="toc" role="directory">
<li><a href="#introduction"><span class="secno">1</span> <span class="content">Introduction</span></a>
<li>
<a href="#user-locale-preferences-features"><span class="secno">2</span> <span class="content">User Locale Preferences Features</span></a>
<ol class="toc">
<li>
<a href="#user-locale-preferences-client-hints"><span class="secno">2.1</span> <span class="content">Client Hints</span></a>
<ol class="toc">
<li><a href="#common-user-preferences"><span class="secno">2.1.1</span> <span class="content">Common User Preferences</span></a>
<li><a href="#other-user-preferences"><span class="secno">2.1.2</span> <span class="content">Other user preferences</span></a>
<li><a href="#client-hint-header-fields"><span class="secno">2.1.3</span> <span class="content"><code>Client Hint</code> Header fields</span></a>
<li><a href="#user-locale-client-hints-example"><span class="secno">2.1.4</span> <span class="content">Usage example</span></a>
</ol>
<li>
<a href="#javascript-api"><span class="secno">2.2</span> <span class="content">JavaScript API</span></a>
<ol class="toc">
<li><a href="#user-local-preferences-javascript-idl"><span class="secno">2.2.1</span> <span class="content">IDL</span></a>
<li><a href="#user-locale-preferences-javascript-api-proposed-syntax"><span class="secno">2.2.2</span> <span class="content">Proposed Syntax</span></a>
<li><a href="#user-locale-preferences-javascript-api-examples"><span class="secno">2.2.3</span> <span class="content">Examples</span></a>
</ol>
</ol>
<li><a href="#privacy-and-security-considerations"><span class="secno">3</span> <span class="content">Privacy and Security Considerations</span></a>
<li>
<a href="#w3c-conformance"><span class="secno"></span> <span class="content">Conformance</span></a>
<ol class="toc">
<li><a href="#w3c-conventions"><span class="secno"></span> <span class="content">Document conventions</span></a>
<li><a href="#w3c-conformant-algorithms"><span class="secno"></span> <span class="content">Conformant Algorithms</span></a>
</ol>
<li>
<a href="#index"><span class="secno"></span> <span class="content">Index</span></a>
<ol class="toc">
<li><a href="#index-defined-here"><span class="secno"></span> <span class="content">Terms defined by this specification</span></a>
<li><a href="#index-defined-elsewhere"><span class="secno"></span> <span class="content">Terms defined by reference</span></a>
</ol>
<li>
<a href="#references"><span class="secno"></span> <span class="content">References</span></a>
<ol class="toc">
<li><a href="#normative"><span class="secno"></span> <span class="content">Normative References</span></a>
</ol>
<li><a href="#idl-index"><span class="secno"></span> <span class="content">IDL Index</span></a>
</ol>
</nav>
<main>
<h2 class="heading settled" data-level="1" id="introduction"><span class="secno">1. </span><span class="content">Introduction</span><a class="self-link" href="#introduction"></a></h2>
<p>User preferences are often system-wide settings (such as in Android, macOS, or Windows). Operating systems allow the user to specify custom overrides for settings such as:</p>
<ul>
<li data-md>
<p>Hour cycle (24-hour or 12-hour time)</p>
<li data-md>
<p>Calendar system</p>
<li data-md>
<p>Measurement unit preferences (metric or imperial)</p>
<li data-md>
<p>Date/time patterns</p>
<li data-md>
<p>Number separators (comma or period)</p>
</ul>
<p>Using this information will let developers improve the accessibility and usability of their websites, and bring the user experience of web applications closer to that of native applications. Client- and server-side applications should consistently share and access locale user preferences that will help solve cases like:</p>
<blockquote>
<p>Alice, an end user, reads en-US but prefers using a 24-hour clock. She has set that preference in her operating system settings. Native apps are able to respect her preference. However, web apps cannot access OS user preferences, so on the Web Platform, Alice sees a 12-hour clock, the default for en-US.</p>
</blockquote>
<blockquote>
<p>Other use cases: NodeJS programs that want to respect the user’s hourCycle preference by passing it in to Intl.DateTimeFormat, other non browser environments.</p>
</blockquote>
<p>For <strong>client-side applications</strong>, the best way to get them is through a browser API that fetches this information from the different platform-specific OS APIs.</p>
<p>For <strong>server-side applications</strong>, one way to get access to this information is via <a data-link-type="biblio" href="#biblio-client-hints" title="HTTP Client Hints">[CLIENT-HINTS]</a> headers on the request.</p>
<figure>
<img alt="Browser conveys permitted OS preferences to server" height="300" src="https://user-images.githubusercontent.com/1572026/182210112-69fb7769-eafa-43ab-bad0-21eb49489d50.png" width="500">
<figcaption>Browser conveys permitted OS preference information to server</figcaption>
</figure>
<h2 class="heading settled" data-level="2" id="user-locale-preferences-features"><span class="secno">2. </span><span class="content">User Locale Preferences Features</span><a class="self-link" href="#user-locale-preferences-features"></a></h2>
<p>We propose to address the above use cases by using a pair of <a data-link-type="biblio" href="#biblio-client-hints" title="HTTP Client Hints">[CLIENT-HINTS]</a> headers and a homologous <a href="#javascript-api">§ 2.2 JavaScript API</a>. Both will be responsible for exposing and negotiating the exchange of user preferences from the OS to the required environment.</p>
<p>We use <a data-link-type="dfn" href="https://cldr.unicode.org/index/bcp47-extension#unicode-extensions-for-bcp-47" id="ref-for-unicode-extensions-for-bcp-47">Unicode Extensions for BCP 47</a> or compatible as the main reference for the base mechanism for delivering user locale preferences. We define new standard <dfn data-dfn-type="dfn" data-export id="locale-preferences"><code>Locale-Preferences</code><a class="self-link" href="#locale-preferences"></a></dfn> Client Hints and <dfn data-dfn-for="NavigatorLocalePreferences" data-dfn-type="dfn" data-export id="navigatorlocalepreferences-navigatorlocalepreferences"><code>navigator.localePreferences</code><a class="self-link" href="#navigatorlocalepreferences-navigatorlocalepreferences"></a></dfn>, that map the user locale preferences using the following steps:</p>
<ol>
<li data-md>
<p>Validate if there is any fingerprinting mechanism and if OS preferences are allowed to be exposed</p>
<li data-md>
<p>Read the available OS preferences</p>
<li data-md>
<p>Return values</p>
</ol>
<h3 class="heading settled" data-level="2.1" id="user-locale-preferences-client-hints"><span class="secno">2.1. </span><span class="content">Client Hints</span><a class="self-link" href="#user-locale-preferences-client-hints"></a></h3>
<p>An <a data-link-type="dfn" href="https://cldr.unicode.org/index/bcp47-extension#http-client-hint" id="ref-for-http-client-hint">HTTP Client Hint</a> is a request header field that is used by HTTP clients to indicate configuration data that can be used by the server to select an appropriate response. It defines an <code>Accept-CH</code> response header that servers can use to advertise their use of request headers for proactive content negotiation. Each new client hint conveys a list of user locale preferences that the server can use to adapt and optimize responses.</p>
<p>The following table suggests <a data-link-type="dfn" href="https://github.com/tc39/ecma402/issues/416#issue-574957588common-user-preferences" id="ref-for-issue-574957588common-user-preferences">common user preferences</a> to be used, and does the correlation from <code>Locale-Preferences</code> Client Hints and <code>navigator.localePreferences</code> to extension keys if they exist, or other values in case table is extended by user demand.</p>
<h4 class="heading settled" data-level="2.1.1" id="common-user-preferences"><span class="secno">2.1.1. </span><span class="content">Common User Preferences</span><a class="self-link" href="#common-user-preferences"></a></h4>
<table>
<tbody>
<tr>
<td>"calendar"
<td><code>ca</code>
<td>buddhist, chinese...
<td>[Calendar system / Calendar algorithm]
<tr>
<td>"currencyFormat"
<td><code>cf</code>
<td>standard, account
<td>Currency Format style, whether to use accounting currency format
<tr>
<td> "collation"
<td> <code>co</code>
<td> standard, search, phonetic...
<td> Collation type, sort order
<tr>
<td> "currencyCode"
<td> <code>cu</code>
<td> ISO 4217 codes
<td> Currency type
<tr>
<td> "emojiStyle"
<td> <code>em</code>
<td> emoji , text, default
<td> Emoji presentation style
<tr>
<td> "firstDayOfTheWeek"
<td> <code>fw</code>
<td> "sun", "mon" ... "sat"
<td> First day of week
<tr>
<td> "hourCycle"
<td> <code>hc</code>
<td> h12 , h23, h11, h24
<td> Hour cycle, i.e., 12-hour or 24-hour clock
<tr>
<td> "measurementSystem"
<td> <code>ms</code>
<td> metric , ussystem , uksystem
<td> Measurement system
<tr>
<td> "measurementUnit"
<td> <code>mu</code>
<td> celsius , kelvin , fahrenhe
<td> <a href="https://github.com/unicode-org/cldr/blob/7942fd82f7e673eb0b27f0bf2025a31572135d95/common/bcp47/measure.xml#L16">Measurement units currently only temperature</a>
<tr>
<td> "numberingSystem"
<td> <code>nu</code>
<td> Unicode script subtag(arabext...) <br>
<td> Numbering system
<tr>
<td> "timeZone"
<td> <code>tz</code>
<td> Unicode short time zone IDs
<td> Time zone
<tr>
<td> "region"
<td> <code>rg</code>
<td> <a href="https://unicode.org/reports/tr35/tr35.html#unicode_region_subtag">Unicode Region Subtag</a>
<td> Region override
<thead>
<tr>
<th>Locale Preferences Name
<th>Extension Key/Unicode Source
<th>Example Values
<th>Description
</table>
<h4 class="heading settled" data-level="2.1.2" id="other-user-preferences"><span class="secno">2.1.2. </span><span class="content">Other user preferences</span><a class="self-link" href="#other-user-preferences"></a></h4>
Other user preferences that might be included based on user research about OS preferences inputs and <a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1308329">#1308329</a>. Although most of the preferences below do not have a 1:1 match with BCP47 extension keys, they are available in ICU/CLDR.
<ul>
<li data-md>
<p>number separator (grouping/decimal)</p>
<li data-md>
<p>date formats short/medium/long/full</p>
<li data-md>
<p>time formats short/medium/long/full</p>
<li data-md>
<p>dayPeriod names</p>
<li data-md>
<p>time display with/without seconds</p>
<li data-md>
<p>flash the time separators</p>
<li data-md>
<p>show dayPeriod</p>
<li data-md>
<p>show the day of the week</p>
<li data-md>
<p>show date</p>
</ul>
<blockquote>
<p class="note" role="note"><span class="marker">Note:</span> The specific preferences ultimately included need to be validated and agreed to by security teams and stakeholders. For this proposal, we consider a subset of possible preferences, sorted into two categories: DateTime and LanguageRegion.</p>
</blockquote>
<h4 class="heading settled" data-level="2.1.3" id="client-hint-header-fields"><span class="secno">2.1.3. </span><span class="content"><code>Client Hint</code> Header fields</span><a class="self-link" href="#client-hint-header-fields"></a></h4>
<p>Servers will receive no information about the user’s locale preferences. Servers can instead opt into receiving such information via new <code>Locale-Preferences</code> Client Hints.</p>
<p>To accomplish this, browsers should introduce a pair of new <code>Client Hint</code> header fields as part of a <a data-link-type="dfn" href="https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-header-structure#structured-header" id="ref-for-structured-header">structured header</a> as defined in <a data-link-type="biblio" href="#biblio-draft-ietf-httpbis-header-structure-19" title="Structured Field Values for HTTP">[draft-ietf-httpbis-header-structure-19]</a>, sent over request whose value is a list of defined user locale preferences.</p>
<p>**<code>Sec-CH-Locale-Preferences-*</code>**</p>
<p>The following table represents the two headers returning individual opted-in <code>Locale-Preferences</code>. These headers group together related sets of preferences in two buckets:</p>
<table>
<tbody>
<tr>
<td><dfn data-dfn-type="dfn" data-export id="sec-ch-locale-preferences-datetime">Sec-CH-Locale-Preferences-DateTime<a class="self-link" href="#sec-ch-locale-preferences-datetime"></a></dfn>
<td> <code>Sec-CH-Locale-Preferences-DateTime</code> : hourCycle="h24";timeZone="CET";...
<tr>
<td><dfn data-dfn-type="dfn" data-export id="sec-ch-locale-preferences-languageregion">Sec-CH-Locale-Preferences-LanguageRegion<a class="self-link" href="#sec-ch-locale-preferences-languageregion"></a></dfn>
<td> <code>Sec-CH-Locale-Preferences-LanguageRegion</code> : calendar="buddhist"; measurementSystem="metric"; ...
<thead>
<tr>
<th left style="text-align:">Client hint
<th left style="text-align:"> Example output
</table>
<h4 class="heading settled" data-level="2.1.4" id="user-locale-client-hints-example"><span class="secno">2.1.4. </span><span class="content">Usage example</span><a class="self-link" href="#user-locale-client-hints-example"></a></h4>
<div class="example" id="example-370e5b09">
<a class="self-link" href="#example-370e5b09"></a>
<ol>
<li data-md>
<p>The client makes an initial request to the server:</p>
</ol>
<pre class="language-http highlight"><c- nf>GET</c-> <c- nn>/</c-> <c- kr>HTTP</c-><c- o>/</c-><c- m>1.1</c->
<c- e>Host</c-><c- o>:</c-> <c- l>example.com</c->
</pre>
<ol start="2">
<li data-md>
<p>The server responds, telling the client via an <code>Accept-CH</code> header (Section 2.2.1 of <a data-link-type="biblio" href="#biblio-rfc8942" title="HTTP Client Hints">[RFC8942]</a>) along with the initial response with <code>Sec-CH-Locale-Preferences-DateTime</code> and the <code>Sec-CH-Locale-Preferences-LanguageRegion</code> Client Hints:</p>
</ol>
<pre class="language-http highlight"><c- kr>HTTP</c-><c- o>/</c-><c- m>1.1</c-> <c- m>200</c-> <c- ne>OK</c->
<c- e>Content-Type</c-><c- o>:</c-> <c- l>text/html</c->
<c- e>Accept-CH</c-><c- o>:</c-> <c- l>Sec-CH-Locale-Preferences-DateTime, Sec-CH-Locale-Preferences-LanguageRegion</c->
</pre>
<ol start="3">
<li data-md>
<p>Subsequent requests to https://example.com will include the following request headers in case the user sets <code>numberingSystem</code> and <code>timeZone</code> values:</p>
</ol>
<pre class="language-http highlight"><c- nf>GET</c-> <c- nn>/</c-> <c- kr>HTTP</c-><c- o>/</c-><c- m>1.1</c->
<c- e>Host</c-><c- o>:</c-> <c- l>example.com</c->
<c- e>Sec-CH-Locale-Preferences-DateTime</c-><c- o>:</c-> <c- l>timeZone="CET"</c->
<c- e>Sec-CH-Locale-Preferences-LanguageRegion</c-><c- o>:</c-> <c- l>numberingSystem="jpan"</c->
</pre>
<ol start="4">
<li data-md>
<p>The server can then tailor the response to the client’s preferences accordingly.</p>
</ol>
</div>
<h3 class="heading settled" data-level="2.2" id="javascript-api"><span class="secno">2.2. </span><span class="content">JavaScript API</span><a class="self-link" href="#javascript-api"></a></h3>
<p>These client hints should also be exposed as JavaScript APIs via <code>navigator.locales</code> as suggested in <a href="https://github.com/tc39/ecma402/issues/68">#68</a> or by creating a new <code>navigator.localePreferences</code> that exposes <code>Locale-Preferences</code> information as below.</p>
<h4 class="heading settled" data-level="2.2.1" id="user-local-preferences-javascript-idl"><span class="secno">2.2.1. </span><span class="content">IDL</span><a class="self-link" href="#user-local-preferences-javascript-idl"></a></h4>
<pre class="idl highlight def"><c- b>dictionary</c-> <dfn class="dfn-paneled idl-code" data-dfn-type="dictionary" data-export id="dictdef-localepreferenceslanguageregion"><code><c- g>LocalePreferencesLanguageRegion</c-></code></dfn> {
<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString" id="ref-for-idl-DOMString"><c- b>DOMString</c-></a> <dfn class="idl-code" data-dfn-for="LocalePreferencesLanguageRegion" data-dfn-type="dict-member" data-export data-type="DOMString " id="dom-localepreferenceslanguageregion-calendar"><code><c- g>calendar</c-></code><a class="self-link" href="#dom-localepreferenceslanguageregion-calendar"></a></dfn>;
<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString" id="ref-for-idl-DOMString①"><c- b>DOMString</c-></a> <dfn class="idl-code" data-dfn-for="LocalePreferencesLanguageRegion" data-dfn-type="dict-member" data-export data-type="DOMString " id="dom-localepreferenceslanguageregion-measurementsystem"><code><c- g>measurementSystem</c-></code><a class="self-link" href="#dom-localepreferenceslanguageregion-measurementsystem"></a></dfn>;
<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString" id="ref-for-idl-DOMString②"><c- b>DOMString</c-></a> <dfn class="idl-code" data-dfn-for="LocalePreferencesLanguageRegion" data-dfn-type="dict-member" data-export data-type="DOMString " id="dom-localepreferenceslanguageregion-measurementunit"><code><c- g>measurementUnit</c-></code><a class="self-link" href="#dom-localepreferenceslanguageregion-measurementunit"></a></dfn>;
<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString" id="ref-for-idl-DOMString③"><c- b>DOMString</c-></a> <dfn class="idl-code" data-dfn-for="LocalePreferencesLanguageRegion" data-dfn-type="dict-member" data-export data-type="DOMString " id="dom-localepreferenceslanguageregion-numberingsystem"><code><c- g>numberingSystem</c-></code><a class="self-link" href="#dom-localepreferenceslanguageregion-numberingsystem"></a></dfn>;
<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString" id="ref-for-idl-DOMString④"><c- b>DOMString</c-></a> <dfn class="idl-code" data-dfn-for="LocalePreferencesLanguageRegion" data-dfn-type="dict-member" data-export data-type="DOMString " id="dom-localepreferenceslanguageregion-region"><code><c- g>region</c-></code><a class="self-link" href="#dom-localepreferenceslanguageregion-region"></a></dfn>;
};
<c- b>dictionary</c-> <dfn class="dfn-paneled idl-code" data-dfn-type="dictionary" data-export id="dictdef-localepreferencesdatetime"><code><c- g>LocalePreferencesDateTime</c-></code></dfn> {
<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString" id="ref-for-idl-DOMString⑤"><c- b>DOMString</c-></a> <dfn class="idl-code" data-dfn-for="LocalePreferencesDateTime" data-dfn-type="dict-member" data-export data-type="DOMString " id="dom-localepreferencesdatetime-dateformat"><code><c- g>dateFormat</c-></code><a class="self-link" href="#dom-localepreferencesdatetime-dateformat"></a></dfn>;
<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString" id="ref-for-idl-DOMString⑥"><c- b>DOMString</c-></a> <dfn class="idl-code" data-dfn-for="LocalePreferencesDateTime" data-dfn-type="dict-member" data-export data-type="DOMString " id="dom-localepreferencesdatetime-timeformats"><code><c- g>timeFormats</c-></code><a class="self-link" href="#dom-localepreferencesdatetime-timeformats"></a></dfn>;
<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString" id="ref-for-idl-DOMString⑦"><c- b>DOMString</c-></a> <dfn class="idl-code" data-dfn-for="LocalePreferencesDateTime" data-dfn-type="dict-member" data-export data-type="DOMString " id="dom-localepreferencesdatetime-timezone"><code><c- g>timeZone</c-></code><a class="self-link" href="#dom-localepreferencesdatetime-timezone"></a></dfn>;
<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString" id="ref-for-idl-DOMString⑧"><c- b>DOMString</c-></a> <dfn class="idl-code" data-dfn-for="LocalePreferencesDateTime" data-dfn-type="dict-member" data-export data-type="DOMString " id="dom-localepreferencesdatetime-hourcycle"><code><c- g>hourCycle</c-></code><a class="self-link" href="#dom-localepreferencesdatetime-hourcycle"></a></dfn>;
<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString" id="ref-for-idl-DOMString⑨"><c- b>DOMString</c-></a> <dfn class="idl-code" data-dfn-for="LocalePreferencesDateTime" data-dfn-type="dict-member" data-export data-type="DOMString " id="dom-localepreferencesdatetime-firstdayoftheweek"><code><c- g>firstDayOfTheWeek</c-></code><a class="self-link" href="#dom-localepreferencesdatetime-firstdayoftheweek"></a></dfn>;
};
<c- b>interface</c-> <c- b>mixin</c-> <dfn class="dfn-paneled idl-code" data-dfn-type="interface" data-export id="navigatorlocalepreferences"><code><c- g>NavigatorLocalePreferences</c-></code></dfn> {
<c- b>readonly</c-> <c- b>attribute</c-> <a data-link-type="idl-name" href="#dictdef-localepreferenceslanguageregion" id="ref-for-dictdef-localepreferenceslanguageregion"><c- n>LocalePreferencesLanguageRegion</c-></a> <dfn class="idl-code" data-dfn-for="NavigatorLocalePreferences" data-dfn-type="attribute" data-export data-readonly data-type="LocalePreferencesLanguageRegion" id="dom-navigatorlocalepreferences-localeregion"><code><c- g>localeRegion</c-></code><a class="self-link" href="#dom-navigatorlocalepreferences-localeregion"></a></dfn>;
<c- b>readonly</c-> <c- b>attribute</c-> <a data-link-type="idl-name" href="#dictdef-localepreferencesdatetime" id="ref-for-dictdef-localepreferencesdatetime"><c- n>LocalePreferencesDateTime</c-></a> <dfn class="idl-code" data-dfn-for="NavigatorLocalePreferences" data-dfn-type="attribute" data-export data-readonly data-type="LocalePreferencesDateTime" id="dom-navigatorlocalepreferences-datetime"><code><c- g>dateTime</c-></code><a class="self-link" href="#dom-navigatorlocalepreferences-datetime"></a></dfn>;
};
<a data-link-type="idl-name" href="https://html.spec.whatwg.org/multipage/system-state.html#navigator" id="ref-for-navigator"><c- n>Navigator</c-></a> <c- b>includes</c-> <a data-link-type="idl-name" href="#navigatorlocalepreferences" id="ref-for-navigatorlocalepreferences"><c- n>NavigatorLocalePreferences</c-></a>;
<a data-link-type="idl-name" href="https://html.spec.whatwg.org/multipage/workers.html#workernavigator" id="ref-for-workernavigator"><c- n>WorkerNavigator</c-></a> <c- b>includes</c-> <a data-link-type="idl-name" href="#navigatorlocalepreferences" id="ref-for-navigatorlocalepreferences①"><c- n>NavigatorLocalePreferences</c-></a>;
</pre>
<h4 class="heading settled" data-level="2.2.2" id="user-locale-preferences-javascript-api-proposed-syntax"><span class="secno">2.2.2. </span><span class="content">Proposed Syntax</span><a class="self-link" href="#user-locale-preferences-javascript-api-proposed-syntax"></a></h4>
<div class="example" id="example-b1c63c51">
<a class="self-link" href="#example-b1c63c51"></a>
<pre class="language-js highlight"><c- c1>// languageAndRegion</c->
navigator<c- p>.</c->localePreferences<c- p>[</c-><c- t>'languageRegion'</c-><c- p>];</c->
navigator<c- p>.</c->localePreferences<c- p>.</c->languageRegion<c- p>;</c->
self<c- p>.</c->navigator<c- p>.</c->localePreferences<c- p>.</c->languageRegion<c- p>;</c->
<c- c1>// Output => => {calendar: "buddhist", measurementSystem: "metric", ... }</c->
<c- c1>// languageAndRegion</c->
navigator<c- p>.</c->localePreferences<c- p>[</c-><c- t>'dateTime'</c-><c- p>];</c->
navigator<c- p>.</c->localePreferences<c- p>.</c->dateTime<c- p>;</c->
self<c- p>.</c->navigator<c- p>.</c->localePreferences<c- p>.</c->dateTime<c- p>;</c->
<c- c1>// Output => { dateFormat: "EEE, d MMM yyyy HH:mm:ss Z", ... }</c->
<c- c1>// Window or WorkerGlobalScope event </c->
window<c- p>.</c->onlocalepreferences <c- o>=</c-> <c- p>(</c->event<c- p>)</c-> <c- p>=></c-> <c- p>{</c->
console<c- p>.</c->log<c- p>(</c-><c- t>'localepreferences event detected!'</c-><c- p>);</c->
<c- p>};</c->
<c- c1>// Or </c->
window<c- p>.</c->addEventListener<c- p>(</c-><c- t>'localepreferences'</c-><c- p>,</c-> <c- p>()</c-> <c- p>=></c-> <c- p>{</c->
console<c- p>.</c->log<c- p>(</c-><c- t>'localepreferences event detected!'</c-><c- p>);</c->
<c- p>});</c->
</pre>
</div>
<h4 class="heading settled" data-level="2.2.3" id="user-locale-preferences-javascript-api-examples"><span class="secno">2.2.3. </span><span class="content">Examples</span><a class="self-link" href="#user-locale-preferences-javascript-api-examples"></a></h4>
<div class="example" id="example-8a397687">
<a class="self-link" href="#example-8a397687"></a>
<p>Use the <code>navigator.localePreferences</code> to populate data with user preferences</p>
<pre class="language-js highlight"><c- c1>// User set locale preferences for calendar , region and hourCycle</c->
navigator<c- p>.</c->localePreferences<c- p>[</c-><c- t>'languageRegion'</c-><c- p>];</c->
navigator<c- p>.</c->localePreferences<c- p>[</c-><c- t>'dateTime'</c-><c- p>];</c->
<c- a>const</c-> preferences <c- o>=</c-> <c- p>(...</c->iterate over needed navigator<c- p>.</c->localePreferences <c- p>)</c->
<c- ow>new</c-> Intl<c- p>.</c->Locale<c- p>(</c-><c- t>'es'</c-> <c- p>,</c-> preferences <c- p>).</c->maximize<c- p>();</c->
<c- c1>// => Locale {..., calendar:"gregory" , region:"GB" , hourCycle:"h11" }</c->
<c- ow>new</c-> Intl<c- p>.</c->DateTimeFormat<c- p>(</c-><c- t>'es'</c-><c- p>,</c-> preferences <c- p>).</c->resolvedOptions<c- p>();</c->
<c- c1>// => {locale: 'es', calendar: 'gregory', numberingSystem: 'latn', timeZone: 'Europe/London', ...}</c->
</pre>
</div>
<h2 class="heading settled" data-level="3" id="privacy-and-security-considerations"><span class="secno">3. </span><span class="content">Privacy and Security Considerations</span><a class="self-link" href="#privacy-and-security-considerations"></a></h2>
<p>There are some concerns that exposing this information would give trackers, advertisers and malicious web services another fingerprinting vector. That said, this information may or may not already be available to a certain extent to such services, based on the host and the user’s settings. The use of <code>Sec-CH-</code> prefix is to forbid access to headers containing <code>Locale Preferences</code> information from JavaScript, and to demarcate them as browser-controlled client hints so that they can be documented and included in requests without triggering CORS preflights.</p>
<p>Client Hints provides a powerful content negotiation mechanism that enables us to adapt content to users' needs without compromising their privacy. It does that by requiring server opt-in, which guarantees that access to the information requires active and tracable action on the server’s side. As such, the mechanism does not increase the web’s current active fingerprinting surface.</p>
<p>The Security Considerations of <a data-link-type="biblio" href="#biblio-client-hints" title="HTTP Client Hints">[CLIENT-HINTS]</a> and <a data-link-type="biblio" href="#biblio-draft-davidben-http-client-hint-reliability-02" title="Client Hint Reliability">[draft-davidben-http-client-hint-reliability-02]</a> likewise apply to this proposal.</p>
</main>
<div data-fill-with="conformance">
<h2 class="no-ref no-num heading settled" id="w3c-conformance"><span class="content">Conformance</span><a class="self-link" href="#w3c-conformance"></a></h2>
<h3 class="no-ref no-num heading settled" id="w3c-conventions"><span class="content">Document conventions</span><a class="self-link" href="#w3c-conventions"></a></h3>
<p>Conformance requirements are expressed
with a combination of descriptive assertions
and RFC 2119 terminology.
The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL”
in the normative parts of this document
are to be interpreted as described in RFC 2119.
However, for readability,
these words do not appear in all uppercase letters in this specification. </p>
<p>All of the text of this specification is normative
except sections explicitly marked as non-normative, examples, and notes. <a data-link-type="biblio" href="#biblio-rfc2119" title="Key words for use in RFCs to Indicate Requirement Levels">[RFC2119]</a> </p>
<p>Examples in this specification are introduced with the words “for example”
or are set apart from the normative text
with <code>class="example"</code>,
like this: </p>
<div class="example" id="w3c-example">
<a class="self-link" href="#w3c-example"></a>
<p>This is an example of an informative example. </p>
</div>
<p>Informative notes begin with the word “Note”
and are set apart from the normative text
with <code>class="note"</code>,
like this: </p>
<p class="note" role="note">Note, this is an informative note.</p>
<h3 class="no-ref no-num heading settled" id="w3c-conformant-algorithms"><span class="content">Conformant Algorithms</span><a class="self-link" href="#w3c-conformant-algorithms"></a></h3>
<p>Requirements phrased in the imperative as part of algorithms
(such as "strip any leading space characters"
or "return false and abort these steps")
are to be interpreted with the meaning of the key word
("must", "should", "may", etc)
used in introducing the algorithm. </p>
<p>Conformance requirements phrased as algorithms or specific steps
can be implemented in any manner,
so long as the end result is equivalent.
In particular, the algorithms defined in this specification
are intended to be easy to understand
and are not intended to be performant.
Implementers are encouraged to optimize. </p>
</div>
<script src="https://www.w3.org/scripts/TR/2021/fixup.js"></script>
<h2 class="no-num no-ref heading settled" id="index"><span class="content">Index</span><a class="self-link" href="#index"></a></h2>
<h3 class="no-num no-ref heading settled" id="index-defined-here"><span class="content">Terms defined by this specification</span><a class="self-link" href="#index-defined-here"></a></h3>
<ul class="index">
<li><a href="#dom-localepreferenceslanguageregion-calendar">calendar</a><span>, in § 2.2.1</span>
<li><a href="#dom-localepreferencesdatetime-dateformat">dateFormat</a><span>, in § 2.2.1</span>
<li><a href="#dom-navigatorlocalepreferences-datetime">dateTime</a><span>, in § 2.2.1</span>
<li><a href="#dom-localepreferencesdatetime-firstdayoftheweek">firstDayOfTheWeek</a><span>, in § 2.2.1</span>
<li><a href="#dom-localepreferencesdatetime-hourcycle">hourCycle</a><span>, in § 2.2.1</span>
<li><a href="#locale-preferences">Locale-Preferences</a><span>, in § 2</span>
<li><a href="#dictdef-localepreferencesdatetime">LocalePreferencesDateTime</a><span>, in § 2.2.1</span>
<li><a href="#dictdef-localepreferenceslanguageregion">LocalePreferencesLanguageRegion</a><span>, in § 2.2.1</span>
<li><a href="#dom-navigatorlocalepreferences-localeregion">localeRegion</a><span>, in § 2.2.1</span>
<li><a href="#dom-localepreferenceslanguageregion-measurementsystem">measurementSystem</a><span>, in § 2.2.1</span>
<li><a href="#dom-localepreferenceslanguageregion-measurementunit">measurementUnit</a><span>, in § 2.2.1</span>
<li><a href="#navigatorlocalepreferences-navigatorlocalepreferences">navigator.localePreferences</a><span>, in § 2</span>
<li><a href="#navigatorlocalepreferences">NavigatorLocalePreferences</a><span>, in § 2.2.1</span>
<li><a href="#dom-localepreferenceslanguageregion-numberingsystem">numberingSystem</a><span>, in § 2.2.1</span>
<li><a href="#dom-localepreferenceslanguageregion-region">region</a><span>, in § 2.2.1</span>
<li><a href="#sec-ch-locale-preferences-datetime">Sec-CH-Locale-Preferences-DateTime</a><span>, in § 2.1.3</span>
<li><a href="#sec-ch-locale-preferences-languageregion">Sec-CH-Locale-Preferences-LanguageRegion</a><span>, in § 2.1.3</span>
<li><a href="#dom-localepreferencesdatetime-timeformats">timeFormats</a><span>, in § 2.2.1</span>