Localization

You can localize your Snap to display your Snap's user interface (UI) text and textual metadata (such as title and description) in the user's language.

Steps

1. Get the user's language

In your Snap's code, determine the user's language by using the snap_getPreferences API method. To call snap_getPreferences, first request the required permission by adding it to the initialPermissions field in your manifest file:

snap.manifest.json

"initialPermissions": {
  "snap_getPreferences": {}
}

Your Snap can then call snap_getPreferences to get the user's language code (for example, en or es).

2. Localize the Snap's UI

Use the user's language code to localize your Snap's UI.

First, create locale files named snap/locales/<language_code>.json, containing content in the following format:

en.json

{
  "locale": "en",
  "messages": {
    "hello": {
      "message": "Hello, world!",
      "description": "The message that is returned when the `hello` method is called."
    }
  }
}

You can then use these files in a localization module. The following is an example module:

import da from "../locales/da.json"
import en from "../locales/en.json"
import nl from "../locales/nl.json"

// Default language, to be used if there is not a valid translation in
// the requested locale.
const FALLBACK_LANGUAGE: Locale = "en"

export const locales = {
  da: da.messages,
  en: en.messages,
  nl: nl.messages,
}

export type Locale = keyof typeof locales

export async function getMessage(id: keyof (typeof locales)[Locale]) {
  const { locale } = (await snap.request({ method: "snap_getPreferences" })) as {
    locale: Locale
  }
  const { message } = locales[locale]?.[id] ?? locales[FALLBACK_LANGUAGE][id]

  return message
}

You can then use the getMessage function in your Snap's code to localize a message, which uses English as the default if the user's locale isn't available.

The following is an example of using getMessage in a Snap's RPC request handler:

index.ts

import { rpcErrors } from "@metamask/rpc-errors"
import type { OnRpcRequestHandler } from "@metamask/snaps-sdk"

import { getMessage } from "./locales"

export const onRpcRequest: OnRpcRequestHandler = async ({ request }) => {
  switch (request.method) {
    case "hello":
      return await getMessage("hello")

    default:
      throw rpcErrors.methodNotFound({
        data: { method: request.method },
      })
  }
}

3. Localize the Snap's manifest file

The Snap manifest file contains textual metadata such as proposedName and description that you can localize to display in the user's language.

The following is an example of a localized manifest file:

snap.manifest.json

{
  "version": "1.1.1",
  "description": "{{ description }}",
  "proposedName": "{{ name }}",
  "source": {
    "shasum": "XXX",
    "locales": ["locales/da.json", "locales/en.json", "locales/nl.json"]
  },
  "initialPermissions": {
    "snap_getPreferences": {}
  },
  "manifestVersion": "0.1"
}

To localize your manifest file, add all available locales to the source.locales section, listing the locale files you created when localizing the Snap's UI. The example locale file provided in Step 2 follows MetaMask's format for manifest localization.

For each field that needs to be localized, replace its text with {{ <fieldName> }}.

When displaying this metadata to the user, MetaMask searches for the proper locale file and replaces the template string with its translation. If it doesn't find the user's locale, MetaMask uses English (en) as the default.

Example

See the @metamask/localization-example-snap package for a full example of localizing a Snap.