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<!DOCTYPE html>
<html>
<head>
<meta charset='utf-8'>
<title>
Payment Request API
</title>
<script src='https://www.w3.org/Tools/respec/respec-w3c' class=
'remove'></script>
<script class='remove'>
var respecConfig = {
github: "w3c/payment-request",
specStatus: "ED",
group: "payments",
formerEditors: [
{
name: "Domenic Denicola",
company: "Google",
w3cid: 52873,
},
{
name: "Adrian Bateman",
company: "Microsoft Corporation",
w3cid: 42763,
},
{
name: "Zach Koch",
company: "Google",
w3cid: 76588,
},
{
name: "Roy McElmurry",
company: "Facebook",
w3cid: 88345,
},
],
editors: [
{
name: "Marcos Cáceres",
url: "https://github.com/marcoscaceres",
companyURL: "https://www.mozilla.com/",
company: "Mozilla",
w3cid: 39125,
},
{
name: "Danyao Wang",
url: "https://github.com/danyao",
company: "Google",
companyURL: "https://www.google.com/",
w3cid: 110796,
},
{
name: "Rouslan Solomakhin",
url: "https://github.com/rsolomakhin",
company: "Google",
companyURL: "https://www.google.com/",
w3cid: 83784,
},
{
name: "Ian Jacobs",
url: "http://www.w3.org/People/Jacobs/",
company: "W3C",
companyURL: "https://www.w3.org/",
w3cid: 2175,
},
],
testSuiteURI: "https://wpt.live/payment-request/",
implementationReportURI:
"https://w3c.github.io/test-results/payment-request/all.html",
caniuse: "payment-request",
lint: {
"check-punctuation": true,
},
doJsonLd: true,
xref: "web-platform",
mdn: true,
};
</script>
<style>
dt { margin-top: 0.75em; }
table { margin-top: 0.75em; border-collapse:collapse; border-style:hidden hidden none hidden }
table thead { border-bottom:solid }
table tbody th:first-child { border-left:solid }
table td, table th { border-left:solid; border-right:solid; border-bottom:solid thin; vertical-align:top; padding:0.2em }
li { margin-top: 0.5em; margin-bottom: 0.5em;}
</style>
</head>
<body data-cite="payment-method-id payment-method-basic-card">
<h1 id="title">
Payment Request API
</h1>
<section id='abstract'>
<p>
This specification standardizes an API to allow merchants (i.e. web
sites selling physical or digital goods) to utilize one or more payment
methods with minimal integration. User agents (e.g., browsers)
facilitate the payment flow between merchant and user.
</p>
</section>
<section id='sotd'>
<p>
The working group maintains <a href=
"https://github.com/w3c/payment-request/issues?utf8=%E2%9C%93&q=is%3Aopen%20is%3Aissue%20-label%3A%22Priority%3A%20Postponed%22%20">
a list of all bug reports that the group has not yet addressed</a>.
Pull requests with proposed specification text for outstanding issues
are strongly encouraged.
</p>
<p>
The working group will demonstrate implementation experience by
producing an <a href=
"https://w3c.github.io/test-results/payment-request/all.html">implementation
report</a>. The report will show two or more independent
implementations passing each mandatory test in the <a href=
"https://wpt.live/payment-request/">test suite</a> (i.e., each test
corresponds to a MUST requirement of the specification).
</p>
<p>
There has been no change in dependencies on other workings groups
during the development of this specification.
</p>
<section>
<h3>
Changes since last publication
</h3>
<p>
Substantive changes to the Payment Request API since the 9 July 2018
version are as follows. The complete list of changes, including all
editorial changes, is viewable in the <a href=
"https://github.com/w3c/payment-request/commits/gh-pages">commit
history</a>.
</p>
<ul>
<li>Added support for notification when the user selects a payment
handler, but before confirming payment. This allows merchant to
update totals, validate acceptance, etc.
</li>
<li>Added support to notify site of billing address selection. This
allows a merchant to update a total (e.g., for VAT in Europe). To
enhance privacy, only some billing address data is returned to the
merchant as long as the user has not confirmed payment.
</li>
<li data-link-for="PaymentResponse">Added support for {{retry()}} and
fine-grain error reporting to the user.
</li>
<li>Added support for merchant validation by the payment handler.
</li>
<li data-link-for="PaymentRequest">Clearer definition of
<a>canMakePayment()</a> and worked to align implementations.
<a>canMakePayment()</a> does not reveal whether payment handler is
primed to pay.
</li>
<li>Removed `languageCode` and `regionCode` from {{PaymentAddress}}.
</li>
<li>Removed `currencySystem`.
</li>
<li>"<a>Payment request is showing</a>" boolean now attached to
top-level browsing context. Previously, only a single payment UI was
allowed to be shown at a time across the whole browser. This now
allows multiple browser tabs to show a payment UI at the same time
(for those payment handlers able to support it).
</li>
<li>Integrated with [[[feature-policy]]].
</li>
<li>Defined handling of multiple applicable modifiers.
</li>
</ul>
</section>
</section>
<section class='informative'>
<h2>
Introduction
</h2>
<p>
This specification describes an API that allows <a>user agents</a>
(e.g., browsers) to act as an intermediary between three parties in a
transaction:
</p>
<ul>
<li>The payee: the merchant that runs an online store, or other party
that requests to be paid.
</li>
<li>The payer: the party that makes a purchase at that online store,
and who authenticates and authorizes payment as required.
</li>
<li>The <dfn>payment method</dfn>: the means that the payer uses to pay
the payee (e.g., a basic card payment). The <dfn>payment method
provider</dfn> establishes the ecosystem to support that payment
method.
</li>
</ul>
<p>
The details of how to fulfill a payment request for a given <a>payment
method</a> is an implementation detail of a <dfn>payment handler</dfn>.
Concretely, each payment handler defines:
</p>
<dl>
<dt>
<dfn>Steps to check if a payment can be made</dfn>:
</dt>
<dd>
How a payment handler determines whether it, or the user, can
potentially "make a payment" is also an implementation detail of a
payment handler. For an example, see the <a data-cite=
"?payment-method-basic-card#steps-to-check-if-a-payment-can-be-made">can
make payment</a> algorithm of [[[?payment-method-basic-card]]].
</dd>
<dt>
<dfn>Steps to respond to a payment request</dfn>:
</dt>
<dd>
Steps that return an object or <a>dictionary</a> that a merchant uses
to process or validate the transaction. The structure of this object
is specific to each <a>payment method</a>. For an example of such an
object, see the {{BasicCardResponse}} dictionary of
[[[?payment-method-basic-card]]].
</dd>
<dt>
<dfn>Steps for when a user changes payment method</dfn> (optional)
</dt>
<dd>
<p>
Steps that describe how to handle the user changing payment method
or monetary instrument (e.g., from a debit card to a credit card)
that results in a <a>dictionary</a> or {{object}} or null.
</p>
</dd>
</dl>
<p>
This API also enables web sites to take advantage of more secure
payment schemes (e.g., tokenization and system-level authentication)
that are not possible with standard JavaScript libraries. This has the
potential to reduce liability for the merchant and helps protect
sensitive user information.
</p>
<section id="goals">
<h2>
Goals and scope
</h2>
<ul>
<li>Allow the user agent to act as intermediary between a merchant,
user, and <a>payment method provider</a>.
</li>
<li>Enable user agents to streamline the user's payment experience by
taking into account user preferences, merchant information, security
considerations, and other factors.
</li>
<li>Standardize (to the extent that it makes sense) the communication
flow between a merchant, user agent, and <a>payment method
provider</a>.
</li>
<li>Enable a <a>payment method provider</a> to bring more secure
payment transactions to the web.
</li>
</ul>
<p>
The following are out of scope for this specification:
</p>
<ul>
<li>Create a new <a>payment method</a>.
</li>
<li>Integrate directly with payment processors.
</li>
</ul>
</section>
</section>
<section class="informative">
<h2>
Examples of usage
</h2>
<p>
In order to use the API, the developer needs to provide and keep track
of a number of key pieces of information. These bits of information are
passed to the {{PaymentRequest}} constructor as arguments, and
subsequently used to update the payment request being displayed to the
user. Namely, these bits of information are:
</p>
<ul>
<li>The |methodData|: A sequence of <a>PaymentMethodData</a>s that
represents the <a>payment methods</a> that the site supports (e.g., "we
support card-based payments, but only Visa and MasterCard credit
cards.").
</li>
<li>The |details|: The details of the transaction, as a
<a>PaymentDetailsInit</a> dictionary. This includes total cost, and
optionally a list of goods or services being purchased, for physical
goods, and shipping options. Additionally, it can optionally include
"modifiers" to how payments are made. For example, "if you pay with a
card belonging to network X, it incurs a US$3.00 processing fee".
</li>
<li>The |options|: Optionally, a list of things as
<a>PaymentOptions</a> that the site needs to deliver the good or
service (e.g., for physical goods, the merchant will typically need a
physical address to ship to. For digital goods, an email will usually
suffice).
</li>
</ul>
<p data-link-for="PaymentRequest">
Once a {{PaymentRequest}} is constructed, it's presented to the end
user via the <a>show()</a> method. The <a>show()</a> returns a promise
that, once the user confirms request for payment, results in a
<a>PaymentResponse</a>.
</p>
<section>
<h3>
Declaring multiple ways of paying
</h3>
<p>
When constructing a new {{PaymentRequest}}, a merchant uses the first
argument (|methodData|) to list the different ways a user can pay for
things (e.g., credit cards, Apple Pay, Google Pay, etc.). More
specifically, the |methodData| sequence contains
<a>PaymentMethodData</a> dictionaries containing the <a>payment
method identifiers</a> for the <a>payment methods</a> that the
merchant accepts and any associated <a>payment method</a> specific
data (e.g., which credit card networks are supported).
</p>
<pre class="example js" title="The `methodData` argument">
const methodData = [
{
supportedMethods: "basic-card",
data: {
supportedNetworks: ["visa", "mastercard"],
},
},
{
supportedMethods: "https://example.com/bobpay",
data: {
merchantIdentifier: "XXXX",
bobPaySpecificField: true,
},
},
];
</pre>
</section>
<section>
<h3>
Describing what is being paid for
</h3>
<p>
When constructing a new {{PaymentRequest}}, a merchant uses the
second argument of the constructor (|details|) to provide the details
of the transaction that the user is being asked to complete. This
includes the total of the order and, optionally, some line items that
can provide a detailed breakdown of what is being paid for.
</p>
<pre class="example js" title="The `details` argument">
const details = {
id: "super-store-order-123-12312",
displayItems: [
{
label: "Sub-total",
amount: { currency: "USD", value: "55.00" },
},
{
label: "Sales Tax",
amount: { currency: "USD", value: "5.00" },
type: "tax"
},
],
total: {
label: "Total due",
// The total is USD$65.00 here because we need to
// add shipping (below). The selected shipping
// costs USD$5.00.
amount: { currency: "USD", value: "65.00" },
},
};
</pre>
</section>
<section>
<h3>
Adding shipping options
</h3>
<p>
Here we see an example of how to add two shipping options to the
|details|.
</p>
<pre class="example js" title="Adding shipping options">
const shippingOptions = [
{
id: "standard",
label: "🚛 Ground Shipping (2 days)",
amount: { currency: "USD", value: "5.00" },
selected: true,
},
{
id: "drone",
label: "🚀 Drone Express (2 hours)",
amount: { currency: "USD", value: "25.00" }
},
];
Object.assign(details, { shippingOptions });
</pre>
</section>
<section>
<h3>
Conditional modifications to payment request
</h3>
<p>
Here we see how to add a processing fee for using a card on a
particular network. Notice that it requires recalculating the total.
</p>
<pre class="example js" title=
"Modifying payment request based on card type">
// Certain cards incur a $3.00 processing fee.
const cardFee = {
label: "Card processing fee",
amount: { currency: "USD", value: "3.00" },
};
// Modifiers apply when the user chooses to pay with
// a card.
const modifiers = [
{
additionalDisplayItems: [cardFee],
supportedMethods: "basic-card",
total: {
label: "Total due",
amount: { currency: "USD", value: "68.00" },
},
data: {
supportedNetworks: networks,
},
},
];
Object.assign(details, { modifiers });
</pre>
</section>
<section>
<h3>
Requesting specific information from the end user
</h3>
<p>
Some financial transactions require a user to provide specific
information in order for a merchant to fulfill a purchase (e.g., the
user's shipping address, in case a physical good needs to be
shipped). To request this information, a merchant can pass a third
optional argument (|options|) to the {{PaymentRequest}} constructor
indicating what information they require. When the payment request is
shown, the user agent will request this information from the end user
and return it to the merchant when the user accepts the payment
request.
</p>
<pre class="example js" title="The `options` argument">
const options = {
requestPayerEmail: false,
requestPayerName: true,
requestPayerPhone: false,
requestShipping: true,
}
</pre>
</section>
<section>
<h3>
Constructing a <code>PaymentRequest</code>
</h3>
<p>
Having gathered all the prerequisite bits of information, we can now
construct a {{PaymentRequest}} and request that the browser present
it to the user:
</p>
<pre class="example js" title="Constructing a `PaymentRequest`">
async function doPaymentRequest() {
try {
const request = new PaymentRequest(methodData, details, options);
// See below for a detailed example of handling these events
request.onshippingaddresschange = ev => ev.updateWith(details);
request.onshippingoptionchange = ev => ev.updateWith(details);
const response = await request.show();
await validateResponse(response);
} catch (err) {
// AbortError, SecurityError
console.error(err);
}
}
async function validateResponse(response) {
try {
const errors = await checkAllValuesAreGood(response);
if (errors.length) {
await response.retry(errors);
return validateResponse(response);
}
await response.complete("success");
} catch (err) {
// Something went wrong...
await response.complete("fail");
}
}
// Must be called as a result of a click
// or some explicit user action.
doPaymentRequest();
</pre>
</section>
<section>
<h3>
Handling events and updating the payment request
</h3>
<p>
Prior to the user accepting to make payment, the site is given an
opportunity to update the payment request in response to user input.
This can include, for example, providing additional shipping options
(or modifying their cost), removing items that cannot ship to a
particular address, etc.
</p>
<pre class="example js" title="Registering event handlers">
const request = new PaymentRequest(methodData, details, options);
// Async update to details
request.onshippingaddresschange = ev => {
ev.updateWith(checkShipping(request));
};
// Sync update to the total
request.onshippingoptionchange = ev => {
// selected shipping option
const { shippingOption } = request;
const newTotal = {
currency: "USD",
label: "Total due",
value: calculateNewTotal(shippingOption),
};
ev.updateWith({ total: newTotal });
};
async function checkShipping(request) {
try {
const json = request.shippingAddress.toJSON();
await ensureCanShipTo(json);
const { shippingOptions, total } = await calculateShipping(json);
return { shippingOptions, total };
} catch (err) {
return { error: `Sorry! we can't ship to your address.` };
}
}
</pre>
</section>
<section>
<h3>
Fine-grained error reporting
</h3>
<p>
A developer can use the <a data-link-for=
"PaymentDetailsUpdate">shippingAddressErrors</a> member of the
<a>PaymentDetailsUpdate</a> dictionary to indicate that there are
validation errors with specific attributes of a {{PaymentAddress}}.
The <a data-link-for="PaymentDetailsUpdate">shippingAddressErrors</a>
member is a <a>AddressErrors</a> dictionary, whose members
specifically demarcate the fields of a <a>physical address</a> that
are erroneous while also providing helpful error messages to be
displayed to the end user.
</p>
<pre class="example js">
request.onshippingaddresschange = ev => {
ev.updateWith(validateAddress(request.shippingAddress));
};
function validateAddress(shippingAddress) {
const error = "Can't ship to this address.";
const shippingAddressErrors = {
city: "FarmVille is not a real place.",
postalCode: "Unknown postal code for your country.",
};
// Empty shippingOptions implies that we can't ship
// to this address.
const shippingOptions = [];
return { error, shippingAddressErrors, shippingOptions };
}
</pre>
</section>
<section data-link-for="PaymentResponse">
<h3>
POSTing payment response back to a server
</h3>
<p>
It's expected that data in a <a>PaymentResponse</a> will be POSTed
back to a server for processing. To make this as easy as possible,
<a>PaymentResponse</a> can use the [=default toJSON steps=] (i.e.,
`.toJSON()`) to serializes the object directly into JSON. This makes
it trivial to POST the resulting JSON back to a server using the
[[[fetch]]]:
</p>
<pre class="example js" title="POSTing with `fetch()`">
async function doPaymentRequest() {
const payRequest = new PaymentRequest(methodData, details, options);
const payResponse = await payRequest.show();
let result = "";
try {
const httpResponse = await fetch("/process-payment", {
method: "POST",
headers: { "Content-Type": "application/json" },
body: payResponse.toJSON(),
});
result = httpResponse.ok ? "success" : "fail";
} catch (err) {
console.error(err);
result = "fail";
}
await payResponse.complete(result);
}
doPaymentRequest();
</pre>
</section>
</section>
<section data-dfn-for="PaymentRequest" data-link-for="PaymentRequest">
<h2>
<dfn>PaymentRequest</dfn> interface
</h2>
<pre class="idl">
[SecureContext, Exposed=Window]
interface PaymentRequest : EventTarget {
constructor(
sequence<PaymentMethodData> methodData,
PaymentDetailsInit details,
optional PaymentOptions options = {}
);
[NewObject]
Promise<PaymentResponse> show(optional Promise<PaymentDetailsUpdate> detailsPromise);
[NewObject]
Promise<void> abort();
[NewObject]
Promise<boolean> canMakePayment();
[NewObject]
Promise<boolean> hasEnrolledInstrument();
readonly attribute DOMString id;
readonly attribute PaymentAddress? shippingAddress;
readonly attribute DOMString? shippingOption;
readonly attribute PaymentShippingType? shippingType;
attribute EventHandler onmerchantvalidation;
attribute EventHandler onshippingaddresschange;
attribute EventHandler onshippingoptionchange;
attribute EventHandler onpaymentmethodchange;
};
</pre>
<div class="note">
<p>
A developer creates a {{PaymentRequest}} to make a payment request.
This is typically associated with the user initiating a payment
process (e.g., by activating a "Buy," "Purchase," or "Checkout"
button on a web site, selecting a "Power Up" in an interactive game,
or paying at a kiosk in a parking structure). The {{PaymentRequest}}
allows developers to exchange information with the <a>user agent</a>
while the user is providing input (up to the point of user approval
or denial of the payment request).
</p>
<p data-link-for="PaymentRequest">
The <a>shippingAddress</a>, <a>shippingOption</a>, and
<a>shippingType</a> attributes are populated during processing if the
{{PaymentOptions/requestShipping}} member is set.
</p>
</div>
<p>
A |request|'s <dfn>payment-relevant browsing context</dfn> is that
{{PaymentRequest}}'s <a>relevant global object</a>'s browsing context's
<a>top-level browsing context</a>. Every <a>payment-relevant browsing
context</a> has a <dfn>payment request is showing</dfn> boolean, which
prevents showing more than one payment UI at a time.
</p>
<p class="Note">
The <a>payment request is showing</a> boolean simply prevents more than
one payment UI being shown in a single browser tab. However, a
<a>payment handler</a> can restrict the <a>user agent</a> to showing
only one payment UI across all browser windows and tabs. Other payment
handlers might allow showing a payment UI across disparate browser
tabs.
</p>
<section>
<h2>
Constructor
</h2>
<p>
The {{PaymentRequest}} is constructed using the supplied sequence of
<a>PaymentMethodData</a> |methodData| including any <a>payment
method</a> specific {{PaymentMethodData/data}}, the
<a>PaymentDetailsInit</a> |details|, and the <a>PaymentOptions</a>
|options|.
</p>
<p data-tests=
"payment-request-constructor.https.html, payment-request-insecure.http.html">
The <code><dfn data-lt=
"PaymentRequest.PaymentRequest()">PaymentRequest(|methodData|,
|details|, |options|)</dfn></code> constructor MUST act as follows:
</p>
<ol data-link-for="PaymentDetailsBase" class="algorithm">
<li>If the <a>current settings object</a>'s [=environment settings
object / responsible document=] is not <a>allowed to use</a> the
"[=payment-feature|payment=]" feature, then [=exception/throw=] a
{{"SecurityError"}} {{DOMException}}.
</li>
<li>Establish the request's id:
<ol>
<li data-tests="payment-request-id-attribute.https.html">If
|details|.{{PaymentDetailsInit/id}} is missing, add an
{{PaymentDetailsInit/id}} member to |details| and set its value
to a <abbr title="Universally Unique Identifier">UUID</abbr>
[[RFC4122]].
</li>
</ol>
</li>
<li>Let |serializedMethodData| be an empty list.
</li>
<li>Process payment methods:
<ol data-link-for="PaymentMethodData">
<li>If the length of the |methodData| sequence is zero, then
[=exception/throw=] a {{TypeError}}, optionally informing the
developer that at least one <a>payment method</a> is required.
</li>
<li>Let |seenPMIs:Set| be the empty [=set=].
</li>
<li>For each |paymentMethod| of |methodData|:
<ol>
<li data-tests=
"payment-request-ctor-pmi-handling.https.html">Run the steps
to <a>validate a payment method identifier</a> with
|paymentMethod|.{{PaymentMethodData/supportedMethods}}. If it
returns false, then throw a {{RangeError}} exception.
Optionally, inform the developer that the payment method
identifier is invalid.
</li>
<li>Let |pmi| be the result of parsing
|paymentMethod|.{{PaymentMethodData/supportedMethods}} with
[=basic URL parser=]:
<ol>
<li>If failure, set |pmi| to
|paymentMethod|.{{PaymentMethodData/supportedMethods}}.
</li>
</ol>
</li>
<li>If |seenPMIs| [=set/contain|contains=] |pmi| throw a
{{RangeError}} {{DOMException}} optionally letting the
developer this [=payment method identifier=] is a duplicate.
</li>
<li>[=set/Append=] |pmi| to |seenPMIs|.
</li>
<li>If the {{PaymentMethodData/data}} member of
|paymentMethod| is missing, let |serializedData| be null.
Otherwise, let |serializedData| be the result of
<a>JSON-serializing</a>
|paymentMethod|.{{PaymentMethodData/data}} into a string.
Rethrow any exceptions.
</li>
<li>If |serializedData| is not null, and if required by the
specification that defines the
|paymentMethod|.<a>supportedMethods</a>:
<ol>
<li>Let |object| be the result of <a data-cite=
"ECMASCRIPT#sec-json.parse">JSON-parsing</a>
|serializedData|.
</li>
<li>
<p>
[=converted to an IDL value|Convert=] |object| to an
IDL value of the type specified by the specification
that defines the
|paymentMethod|.<a>supportedMethods</a> (e.g.,
{{BasicCardRequest}} in the case of
[[[?payment-method-basic-card]]]). Rethrow any
exceptions.
</p>
<p class="note">
This step assures that any IDL type conversion errors
are caught as early as possible.
</p>
</li>
</ol>
</li>
<li>Add the tuple
(|paymentMethod|.{{PaymentMethodData/supportedMethods}},
|serializedData|) to |serializedMethodData|.
</li>
</ol>
</li>
</ol>
</li>
<li>Process the total:
<ol>
<li data-tests=
"payment-request-ctor-currency-code-checks.https.html">
<a>Check and canonicalize total amount</a>
|details|.{{PaymentDetailsInit/total}}.{{PaymentItem/amount}}.
Rethrow any exceptions.
</li>
</ol>
</li>
<li>If the <a>displayItems</a> member of |details| is present, then
for each |item| in |details|.<a>displayItems</a>:
<ol>
<li data-tests=
"payment-request-ctor-currency-code-checks.https.html">
<a>Check and canonicalize amount</a>
|item|.{{PaymentItem/amount}}. Rethrow any exceptions.
</li>
</ol>
</li>
<li>Let |selectedShippingOption| be null.
</li>
<li>If the {{PaymentOptions/requestShipping}} member of |options| is
present and set to true, process shipping options:
<ol>
<li>Let |options:PaymentShippingOption| be an empty
<code><a>sequence</a></code><<a>PaymentShippingOption</a>>.
</li>
<li>If the <a>shippingOptions</a> member of |details| is present,
then:
<ol data-link-for="PaymentShippingOption">
<li>Let |seenIDs| be an empty set.
</li>
<li>For each |option| in |details|.<a data-link-for=
"PaymentDetailsBase">shippingOptions</a>:
<ol>
<li data-tests=
"payment-request-ctor-currency-code-checks.https.html">
<a>Check and canonicalize amount</a>
|item|.{{PaymentItem/amount}}. Rethrow any exceptions.
</li>
<li>If |seenIDs| contains |option|.<a>id</a>, then throw
a {{TypeError}}. Optionally, inform the developer that
shipping option IDs must be unique.
</li>
<li>Otherwise, append |option|.<a>id</a> to |seenIDs|.
</li>
<li>If |option|.<a>selected</a> is true, then set
|selectedShippingOption| to |option|.<a>id</a>.
</li>
</ol>
</li>
</ol>
</li>
<li>Set |details|.{{PaymentDetailsBase/shippingOptions}} to
|options|.
</li>
</ol>
</li>
<li>Let |serializedModifierData| be an empty list.
</li>
<li data-link-for="PaymentDetailsBase">Process payment details
modifiers:
<ol>
<li>Let |modifiers| be an empty
<code><a>sequence</a></code><<a>PaymentDetailsModifier</a>>.
</li>
<li>If the <a>modifiers</a> member of |details| is present, then:
<ol>
<li>Set |modifiers| to |details|.<a>modifiers</a>.
</li>
<li>For each |modifier| of |modifiers|:
<ol>
<li>If the {{PaymentDetailsModifier/total}} member of
|modifier| is present, then:
<ol>
<li data-tests=
"payment-request-ctor-currency-code-checks.https.html">
<a>Check and canonicalize total amount</a>
|modifier|.{{PaymentDetailsModifier/total}}.{{PaymentItem/amount}}.
Rethrow any exceptions.
</li>
</ol>
</li>
<li>If the
{{PaymentDetailsModifier/additionalDisplayItems}} member
of |modifier| is present, then for each |item| of
|modifier|.{{PaymentDetailsModifier/additionalDisplayItems}}:
<ol>
<li data-tests=
"payment-request-ctor-currency-code-checks.https.html">
<a>Check and canonicalize amount</a>
|item|.{{PaymentItem/amount}}. Rethrow any
exceptions.
</li>
</ol>
</li>
<li>If the {{PaymentDetailsModifier/data}} member of
|modifier| is missing, let |serializedData| be null.
Otherwise, let |serializedData| be the result of
<a>JSON-serializing</a>
|modifier|.{{PaymentDetailsModifier/data}} into a string.
Rethrow any exceptions.
</li>
<li>Add the tuple
(|modifier|.{{PaymentDetailsModifier/supportedMethods}},
|serializedData|) to |serializedModifierData|.
</li>
<li>Remove the {{PaymentDetailsModifier/data}} member of
|modifier|, if it is present.
</li>
</ol>
</li>
</ol>
</li>
<li>Set |details|.{{PaymentDetailsBase/modifiers}} to
|modifiers|.
</li>
</ol>
</li>
<li>Let |request:PaymentRequest| be a new {{PaymentRequest}}.
</li>
<li>Set |request|.[=PaymentRequest/[[handler]]=] to `null`.
</li>
<li>Set |request|.[=PaymentRequest/[[options]]=] to |options|.
</li>
<li>Set |request|.{{PaymentRequest/[[state]]}} to
"[=state/created=]".
</li>
<li>Set |request|.{{PaymentRequest/[[updating]]}} to false.
</li>
<li>Set |request|.[=PaymentRequest/[[details]]=] to |details|.
</li>
<li>Set |request|.[=PaymentRequest/[[serializedModifierData]]=] to
|serializedModifierData|.
</li>
<li>Set |request|.[=PaymentRequest/[[serializedMethodData]]=] to
|serializedMethodData|.
</li>
<li>Set |request|.{{PaymentRequest/[[response]]}} to null.
</li>
<li>Set the value of |request|'s {{PaymentRequest/shippingOption}}
attribute to |selectedShippingOption|.
</li>
<li>Set the value of the {{PaymentRequest/shippingAddress}} attribute
on |request| to null.
</li>
<li>If |options|.{{PaymentOptions/requestShipping}} is set to true,
then set the value of the {{PaymentRequest/shippingType}} attribute
on |request| to |options|.{{PaymentOptions/shippingType}}. Otherwise,
set it to null.
</li>
<li>Return |request|.
</li>
</ol>
</section>
<section data-dfn-for="PaymentRequest" data-link-for="PaymentRequest">
<h2>
<dfn>id</dfn> attribute
</h2>
<p data-tests="payment-request-id-attribute.https.html">
When getting, the <a>id</a> attribute returns this
{{PaymentRequest}}'s
[=PaymentRequest/[[details]]=].{{PaymentDetailsInit/id}}.
</p>
<div class="note">
<p>
For auditing and reconciliation purposes, a merchant can associate
a unique identifier for each transaction with the
{{PaymentDetailsInit/id}} attribute.
</p>
</div>
</section>
<section data-dfn-for="PaymentRequest" data-link-for="PaymentRequest">
<h2>
<dfn>show()</dfn> method
</h2>
<div class="note">
<p>
The <a>show()</a> method is called when a developer wants to begin
user interaction for the payment request. The <a>show()</a> method
returns a {{Promise}} that will be resolved when the <a>user
accepts the payment request</a>. Some kind of user interface will
be presented to the user to facilitate the payment request after
the <a>show()</a> method returns.
</p>
<p>
Each payment handler controls what happens when multiple browsing
context simultaneously call the <a>show()</a> method. For instance,
some payment handlers will allow multiple payment UIs to be shown
in different browser tabs/windows. Other payment handlers might
only allow a single payment UI to be shown for the entire user
agent.
</p>
</div>
<p data-tests="payment-request-show-method.https.html">
The <code>show(optional |detailsPromise|)</code> method MUST act as
follows:
</p>
<ol class="algorithm">
<li data-tests=
"payment-request-show-method.https.html, show-method-postmessage-manual.https.html">
If the [=relevant global object=] of [=this=] does not have
[=transient activation=], return [=a promise rejected with=] with a
{{"SecurityError"}} {{DOMException}}.
</li>
<li>Let |request:PaymentRequest| be the <a>context object</a>.
</li>
<li>Let |document| be |request|'s <a>relevant global object</a>'s <a>
associated <code>Document</code></a>.
</li>
<li data-tests="rejects_if_not_active.https.html">If |document| is
not [=Document/fully active=], then return <a>a promise rejected
with</a> an {{"AbortError"}} {{DOMException}}.
</li>
<li>
<p>
Optionally, if the <a>user agent</a> wishes to disallow the call
to <a>show()</a> to protect the user, then return a promise
rejected with a {{"SecurityError"}} {{DOMException}}. For
example, the <a>user agent</a> may limit the rate at which a page
can call <a>show()</a>, as described in section <a href=
"#privacy"></a>.
</p>
</li>
<li>If |request|.{{PaymentRequest/[[state]]}} is not
"[=state/created=]" then return <a>a promise rejected with</a> an