This specification defines payment method identifiers and how they are validated, and, where applicable, minted and formally registered with the W3C. Other specifications (e.g., the Payment Request API) make use of these identifiers to facilitate monetary transactions on the web platform.

The working group will demonstrate implementation experience by producing an implementation report. The report will show two or more independent implementations passing each mandatory test in the test suite (i.e., each test corresponds to a MUST requirement of the specification).

There has been no change in dependencies on other workings groups during the development of this specification.

Please file any issues with this specification in the payment method identifiers repository on GitHub.

Payment method identifiers (PMIs)

A payment method identifier is either a:

Validity

Specifications that rely on payment method identifiers MUST specify their own rules for handling invalid payment method identifiers.

The steps to validate a payment method identifier with a string pmi are given by the following algorithm. It returns true if the pmi is valid.

  1. Let url be the result of running the basic URL parser with pmi.
  2. If url is failure, validate a standardized payment method identifier with pmi and return the result.
  3. Otherwise, validate a URL-based payment method identifier passing url and return the result.

URL-based payment method identifiers

A URL-based payment method identifier is a URL that is valid as per the steps to validate a URL-based payment method identifier.

Developers wanting to use a URL-based payment method identifier for a third party payment handler are encouraged to read the Payment Method Best Practice document.

Validation

The steps to validate a URL-based payment method identifier are given by the following algorithm. The algorithm takes a URL url as input and returns true if the URL is valid:

  1. If url's scheme is not "https", return false.
  2. If url's username or password is not the empty string, return false.
  3. Otherwise, return true. 
          const valid = [
            {
              supportedMethods: "https://example.com/pay",
            },
            {
              supportedMethods: "https://example.com/pay?version=1",
            },
            {
              supportedMethods: "https://example.com/pay/version/1",
            },
          ];

          const invalid = [
            {
              // ❌ Uses http://, a username, and a password.
              supportedMethods: "http://username:password@example.com/pay",
            },
            {
              // ❌ Uses unknown URI scheme.
              supportedMethods: "unknown://example.com/pay",
            },
          ];

Comparison

User agents MUST perform comparisons of URL-based payment method identifiers using equals. [[URL]]

Fetching (dereferencing)

It is OPTIONAL for user agents to fetch a URL-based payment method identifier.

Standardized payment method identifiers

A standardized payment method identifier is a string that represents a standardized payment method.

The syntax of a standardized payment method identifier is given by the following [[ABNF]]: 

        stdpmi = part *( "-" part )
        part = 1loweralpha *( DIGIT / loweralpha )
        loweralpha =  %x61-7A

User agents MAY support zero or more standardized payment method identifiers listed in section .

Validity

The steps to validate a standardized payment method identifier are given by the following algorithm. The algorithm takes a string as input and returns true if the identifier is valid:

  1. Return true if string conforms to the syntax of a standardized payment method identifier. Otherwise, return false.

Comparison

For standardized payment method identifiers, user agents MUST compare strings in a case-sensitive manner (code point for code point).

Registry of standardized payment methods

A standardized payment method is a payment method that has undergone standardization at the W3C, and is listed in this registry.

The Working Group has minted the following standardized payment method identifiers:

"basic-card"
The Payment Method: Basic Card specification.

URL-based PMI and third-party payment handlers

Developers wanting to use a URL-based payment method identifier for a third party payment handler are encouraged to read the Payment Method Manifest specification and the Payment Method Best Practice wiki page. Together, these documents describe how to manage the ecosystem of authorized payment handlers for a payment method, including just-in-time payment handler installation by the browser.

Privacy and security consideration

There are no known privacy or security concerns to be taken into considerations at this time.