--- title: Localization description: The API for localizing your extension. api_version: 2025-10 api_name: customer-account-ui-extensions source_url: html: >- https://shopify.dev/docs/api/customer-account-ui-extensions/latest/apis/localization md: >- https://shopify.dev/docs/api/customer-account-ui-extensions/latest/apis/localization.md --- # LocalizationAPI The API for localizing your extension. ## StandardApi The base API object provided to this and other `customer-account` extension targets. * i18n I18n required Utilities for translating content and formatting values according to the current `localization` of the user. * localization Localization required Details about the language of the buyer. ### I18n * formatCurrency Returns a localized currency value. This function behaves like the standard \`Intl.NumberFormat()\` with a style of \`currency\` applied. It uses the buyer's locale by default. ```ts (number: number | bigint, options?: { inExtensionLocale?: boolean; } & NumberFormatOptions) => string ``` * formatDate Returns a localized date value. This function behaves like the standard \`Intl.DateTimeFormatOptions()\` and uses the buyer's locale by default. Formatting options can be passed in as options. ```ts (date: Date, options?: { inExtensionLocale?: boolean; } & DateTimeFormatOptions) => string ``` * formatNumber Returns a localized number. This function behaves like the standard \`Intl.NumberFormat()\` with a style of \`decimal\` applied. It uses the buyer's locale by default. ```ts (number: number | bigint, options?: { inExtensionLocale?: boolean; } & NumberFormatOptions) => string ``` * translate Returns translated content in the buyer's locale, as supported by the extension. - \`options.count\` is a special numeric value used in pluralization. - The other option keys and values are treated as replacements for interpolation. - If the replacements are all primitives, then \`translate()\` returns a single string. - If replacements contain UI components, then \`translate()\` returns an array of elements. ```ts I18nTranslate ``` ```ts export interface I18n { /** * Returns a localized number. * * This function behaves like the standard `Intl.NumberFormat()` * with a style of `decimal` applied. It uses the buyer's locale by default. * * @param options.inExtensionLocale - if true, use the extension's locale */ formatNumber: ( number: number | bigint, options?: {inExtensionLocale?: boolean} & Intl.NumberFormatOptions, ) => string; /** * Returns a localized currency value. * * This function behaves like the standard `Intl.NumberFormat()` * with a style of `currency` applied. It uses the buyer's locale by default. * * @param options.inExtensionLocale - if true, use the extension's locale */ formatCurrency: ( number: number | bigint, options?: {inExtensionLocale?: boolean} & Intl.NumberFormatOptions, ) => string; /** * Returns a localized date value. * * This function behaves like the standard `Intl.DateTimeFormatOptions()` and uses * the buyer's locale by default. Formatting options can be passed in as * options. * * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DateTimeFormat0 * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DateTimeFormat#using_options * * @param options.inExtensionLocale - if true, use the extension's locale */ formatDate: ( date: Date, options?: {inExtensionLocale?: boolean} & Intl.DateTimeFormatOptions, ) => string; /** * Returns translated content in the buyer's locale, * as supported by the extension. * * - `options.count` is a special numeric value used in pluralization. * - The other option keys and values are treated as replacements for interpolation. * - If the replacements are all primitives, then `translate()` returns a single string. * - If replacements contain UI components, then `translate()` returns an array of elements. */ translate: I18nTranslate; } ``` ### I18nTranslate This defines the i18n.translate() signature. ```ts export interface I18nTranslate { /** * This returns a translated string matching a key in a locale file. * * @example translate("banner.title") */ ( key: string, options?: {[placeholderKey: string]: ReplacementType | string | number}, ): ReplacementType extends string | number ? string : (string | ReplacementType)[]; } ``` ### Localization * country The country context of the buyer sees in the customer account. It will update if the buyer changes the country in the customer account If the country is unknown, then the value is undefined. ```ts SubscribableSignalLike ``` * extensionLanguage This is the buyer's language, as supported by the extension. If the buyer's actual language is not supported by the extension, this is the fallback locale used for translations. For example, if the buyer's language is 'fr-CA' but your extension only supports translations for 'fr', then the \`isoCode\` for this language is 'fr'. If your extension does not provide french translations at all, this value is the default locale for your extension (that is, the one matching your .default.json file). ```ts SubscribableSignalLike ``` * language The language the buyer sees in the customer account hub. ```ts SubscribableSignalLike ``` ```ts export interface Localization { /** * The language the buyer sees in the customer account hub. */ language: SubscribableSignalLike; /** * This is the buyer's language, as supported by the extension. * If the buyer's actual language is not supported by the extension, * this is the fallback locale used for translations. * * For example, if the buyer's language is 'fr-CA' but your extension * only supports translations for 'fr', then the `isoCode` for this * language is 'fr'. If your extension does not provide french * translations at all, this value is the default locale for your * extension (that is, the one matching your .default.json file). */ extensionLanguage: SubscribableSignalLike; /** * The country context of the buyer sees in the customer account. * It will update if the buyer changes the country in the customer account * If the country is unknown, then the value is undefined. */ country: SubscribableSignalLike; } ``` ### SubscribableSignalLike Represents a read-only value managed on the main thread that an extension can subscribe to. Example: Checkout uses this to manage the state of an object and communicate state changes to extensions running in a sandboxed web worker. This interface is compatible with \[Preact's ReadonlySignal]\(https://github.com/preactjs/signals/blob/a023a132a81bd4ba4a0bebb8cbbeffbd8c8bbafc/packages/core/src/index.ts#L700-L709). Some fields are deprecated but still supported for backwards compatibility. In version 2025-10, \[\`StatefulRemoteSubscribable\`]\(https://github.com/Shopify/remote-dom/blob/03929aa8418a89d41d294005f219837582718df8/packages/async-subscription/src/types.ts#L17) was replaced with \`ReadonlySignalLike\`. Checkout will remove the old fields some time in the future. * current ```ts T ``` * destroy ```ts () => Promise ``` * subscribe ```ts (fn: (value: T) => void) => () => void ``` * value ```ts T ``` ```ts export interface SubscribableSignalLike extends ReadonlySignalLike { /** * @deprecated Use `.value` instead. */ readonly current: T; /** * @deprecated No longer needed. Use Preact Signal management instead. */ destroy(): Promise; } ``` ### Country * isoCode The ISO-3166-1 code for this country. ```ts CountryCode ``` ```ts export interface Country { /** * The ISO-3166-1 code for this country. * @see https://www.iso.org/iso-3166-country-codes.html */ isoCode: CountryCode; } ``` ### CountryCode ```ts 'AC' | 'AD' | 'AE' | 'AF' | 'AG' | 'AI' | 'AL' | 'AM' | 'AN' | 'AO' | 'AR' | 'AT' | 'AU' | 'AW' | 'AX' | 'AZ' | 'BA' | 'BB' | 'BD' | 'BE' | 'BF' | 'BG' | 'BH' | 'BI' | 'BJ' | 'BL' | 'BM' | 'BN' | 'BO' | 'BQ' | 'BR' | 'BS' | 'BT' | 'BV' | 'BW' | 'BY' | 'BZ' | 'CA' | 'CC' | 'CD' | 'CF' | 'CG' | 'CH' | 'CI' | 'CK' | 'CL' | 'CM' | 'CN' | 'CO' | 'CR' | 'CU' | 'CV' | 'CW' | 'CX' | 'CY' | 'CZ' | 'DE' | 'DJ' | 'DK' | 'DM' | 'DO' | 'DZ' | 'EC' | 'EE' | 'EG' | 'EH' | 'ER' | 'ES' | 'ET' | 'FI' | 'FJ' | 'FK' | 'FO' | 'FR' | 'GA' | 'GB' | 'GD' | 'GE' | 'GF' | 'GG' | 'GH' | 'GI' | 'GL' | 'GM' | 'GN' | 'GP' | 'GQ' | 'GR' | 'GS' | 'GT' | 'GW' | 'GY' | 'HK' | 'HM' | 'HN' | 'HR' | 'HT' | 'HU' | 'ID' | 'IE' | 'IL' | 'IM' | 'IN' | 'IO' | 'IQ' | 'IR' | 'IS' | 'IT' | 'JE' | 'JM' | 'JO' | 'JP' | 'KE' | 'KG' | 'KH' | 'KI' | 'KM' | 'KN' | 'KP' | 'KR' | 'KW' | 'KY' | 'KZ' | 'LA' | 'LB' | 'LC' | 'LI' | 'LK' | 'LR' | 'LS' | 'LT' | 'LU' | 'LV' | 'LY' | 'MA' | 'MC' | 'MD' | 'ME' | 'MF' | 'MG' | 'MK' | 'ML' | 'MM' | 'MN' | 'MO' | 'MQ' | 'MR' | 'MS' | 'MT' | 'MU' | 'MV' | 'MW' | 'MX' | 'MY' | 'MZ' | 'NA' | 'NC' | 'NE' | 'NF' | 'NG' | 'NI' | 'NL' | 'NO' | 'NP' | 'NR' | 'NU' | 'NZ' | 'OM' | 'PA' | 'PE' | 'PF' | 'PG' | 'PH' | 'PK' | 'PL' | 'PM' | 'PN' | 'PS' | 'PT' | 'PY' | 'QA' | 'RE' | 'RO' | 'RS' | 'RU' | 'RW' | 'SA' | 'SB' | 'SC' | 'SD' | 'SE' | 'SG' | 'SH' | 'SI' | 'SJ' | 'SK' | 'SL' | 'SM' | 'SN' | 'SO' | 'SR' | 'SS' | 'ST' | 'SV' | 'SX' | 'SY' | 'SZ' | 'TA' | 'TC' | 'TD' | 'TF' | 'TG' | 'TH' | 'TJ' | 'TK' | 'TL' | 'TM' | 'TN' | 'TO' | 'TR' | 'TT' | 'TV' | 'TW' | 'TZ' | 'UA' | 'UG' | 'UM' | 'US' | 'UY' | 'UZ' | 'VA' | 'VC' | 'VE' | 'VG' | 'VN' | 'VU' | 'WF' | 'WS' | 'XK' | 'YE' | 'YT' | 'ZA' | 'ZM' | 'ZW' | 'ZZ' ``` ### Language * isoCode The BCP-47 language tag. It may contain a dash followed by an ISO 3166-1 alpha-2 region code. ```ts string ``` ```ts export interface Language { /** * The BCP-47 language tag. It may contain a dash followed by an ISO 3166-1 alpha-2 region code. * * @example 'en' for English, or 'en-US' for English local to United States. * @see https://en.wikipedia.org/wiki/IETF_language_tag * @see https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2 */ isoCode: string; } ``` ## Examples