Snaps API

Snaps can communicate with and modify the functionality of MetaMask using the Snaps API. To call each method (except the interactive UI methods), you must first request permission in the Snap manifest file.

note

See the Wallet API for Snaps for methods that dapps can call to communicate with Snaps.

snap_dialog

Displays a dialog in the MetaMask UI.

Parameters

An object containing the contents of the dialog:

• type - The type of dialog. Possible values are:
  • "alert" - An alert that can only be acknowledged.
  • "confirmation" - A confirmation that can be accepted or rejected.
  • "prompt" - A prompt where the user can enter a text response.
• One of:
  • content - The content of the alert, as a custom UI component.
  • id - The ID of an interactive interface.
• placeholder - Only used for "prompt" dialogs. Text that will be in the input field when nothing is typed.

Returns

Return value depends on the dialog type:

• "alert" - None.
• "confirmation" - true if the confirmation was accepted, false otherwise.
• "prompt" - The text entered by the user if the prompt was submitted or null if the prompt was rejected or closed. If the user does not enter any text and submits the prompt, the value is an empty string.

Example

index.js

import { panel, text, heading } from "@metamask/snaps-sdk";

const walletAddress = await snap.request({
  method: "snap_dialog",
  params: {
    type: "prompt",
    content: panel([
      heading("What is the wallet address?"),
      text("Please enter the wallet address to be monitored"),
    ]),
    placeholder: "0x123...",
  },
});

// walletAddress will be a string containing the address entered by the user.

snap_getBip32Entropy

important

If you call this method, you receive the user's parent key for the derivation path they request. You're managing the user's keys and assets on their behalf. Their safety is your responsibility.

Gets the SLIP-10 key for the path and curve specified by the method name.

This method is designed to be used with the @metamask/key-tree module. @metamask/key-tree can help you get the extended private keys for user addresses, but it's your responsibility to know how to use those keys to, for example, derive an address for the relevant protocol or sign a transaction for the user.

Parameters

An object containing:

• path - An array, starting with m, containing the BIP-32 derivation path to the key to retrieve. For example, ["m", "44'", "60'"].
• curve - The curve to use for the key derivation. Must be "ed25519" or "secp256k1".

Returns

An object representing the SLIP-10 HD tree node and containing its corresponding key material:

• depth - The 0-indexed path depth of the node.
• parentFingerprint - The fingerprint of the parent key, or 0 if this is a master node.
• index - The index of the node, or 0 if this is a master node.
• privateKey - The private key of the node.
• publicKey - The public key of the node.
• chainCode - The chain code of the node.
• curve - The name of the curve used by the node: "ed25519" or "secp256k1".

Example

Manifest file

snap.manifest.json

"initialPermissions": {
  "snap_getBip32Entropy": [
    {
      "path": ["m", "44'", "3'"],
      "curve": "secp256k1" // Or "ed25519"
    }
  ]
}

JavaScript

index.js

import { SLIP10Node } from "@metamask/key-tree";

// This example uses Dogecoin, which has a derivation path starting with m/44'/3'.
const dogecoinNode = await snap.request({
  method: "snap_getBip32Entropy",
  params: {
    // The path and curve must be specified in the initial permissions.
    path: ["m", "44'", "3'"],
    curve: "secp256k1",
  },
});

// Next, create an instance of a SLIP-10 node for the Dogecoin node.
const dogecoinSlip10Node = await SLIP10Node.fromJSON(dogecoinNode);

// m/44'/3'/0'
const accountKey0 = await dogecoinSlip10Node.derive(["bip32:0'"]);

// m/44'/3'/1'
const accountKey1 = await dogecoinSlip10Node.derive(["bip32:1'"]);

// Now, you can ask the user to sign transactions, etc.

snap_getBip32PublicKey

Gets the BIP-32 public key for the derivation path specified by the path parameter. Note that this returns the public key, not the extended public key (xpub), or Ethereum address.

Parameters

An object containing:

• path - An array, starting with m, containing the BIP-32 derivation path to the public key to retrieve. For example, ["m", "44'", "60'"].
• curve - The curve to use for the key derivation. Must be "ed25519" or "secp256k1".
• compressed - Indicates whether the public key should be compressed. The default is false.

Returns

The public key as hexadecimal string.

Example

Manifest file

snap.manifest.json

"initialPermissions": {
  "snap_getBip32PublicKey": [
    {
      "path": ["m", "44'", "3'", "0'", "0", "0"],
      "curve": "secp256k1"
    }
  ]
}

JavaScript

index.js

// This example uses Dogecoin, which has a derivation path starting with m/44'/3'.
const dogecoinPublicKey = await snap.request({
  method: "snap_getBip32PublicKey",
  params: {
    // The path and curve must be specified in the initial permissions.
    path: ["m", "44'", "3'", "0'", "0", "0"],
    curve: "secp256k1",
    compressed: false,
  },
});

// "0x..."
console.log(dogecoinPublicKey);

snap_getBip44Entropy

important

If you call this method, you receive the user's parent key for the protocol they request. You're managing the user's keys and assets on their behalf. Their safety is your responsibility.

Gets the BIP-44 coin_type key for the coin_type number specified by the method name. See SLIP-44 for the list of available protocols and their coin_type values.

This method is designed to be used with the @metamask/key-tree module. @metamask/key-tree can help you get the extended private keys for user addresses, but it's your responsibility to know how to use those keys to, for example, derive an address for the relevant protocol or sign a transaction for the user.

Parameters

An object containing coinType, the BIP-44 coin type to get the entropy for.

caution

Coin type 60 is reserved for MetaMask externally owned accounts and blocked for Snaps. If you wish to connect to MetaMask accounts in a Snap, use endowment:ethereum-provider and eth_requestAccounts.

Returns

An object representing the BIP-44 coin_type HD tree node and containing its corresponding key material:

• coin_type - The BIP-44 coin type value of the node.
• depth - The 0-indexed BIP-44 path depth of the node. Since this is a coin_type node, the depth is 2.
• privateKey - The hexadecimal-encoded string representation of the private key for the node.
• publicKey - The hexadecimal-encoded string representation of the public key for the node.
• chainCode - The hexadecimal-encoded string representation of the chain code for the node.
• path - A human-readable representation of the BIP-44 HD tree path of the node. Since this is a coin_type node, the path is of the form m/44'/coin_type'.

Example

Manifest file

snap.manifest.json

"initialPermissions": {
  "snap_getBip44Entropy": [
    {
      "coinType": 3
    }
  ]
}

JavaScript

index.js

import { getBIP44AddressKeyDeriver } from "@metamask/key-tree";

// This example uses Dogecoin, which has coin_type 3.
const dogecoinNode = await snap.request({
  method: "snap_getBip44Entropy",
  params: {
    coinType: 3,
  },
});

// Next, create an address key deriver function for the Dogecoin coin_type node.
// In this case, its path is: m/44'/3'/0'/0/address_index
const deriveDogecoinAddress = await getBIP44AddressKeyDeriver(dogecoinNode);

// These are BIP-44 nodes containing the extended private keys for the respective derivation paths.

// m/44'/3'/0'/0/0
const addressKey0 = await deriveDogecoinAddress(0);

// m/44'/3'/0'/0/1
const addressKey1 = await deriveDogecoinAddress(1);

// Now, you can ask the user to sign transactions, etc.

snap_getClientStatus

Gets the locked status of the Snaps client.

It is useful to check if MetaMask is locked in the following situations:

• When running background operations that require MetaMask to be unlocked, for example, accessing encrypted state. If MetaMask is locked, the user gets an unexpected password request.
• When displaying a dialog. Dialogs do not work when MetaMask is locked.

Returns

true if MetaMask is locked, false if MetaMask is unlocked.

Example

index.js

import type { OnCronjobHandler } from "@metamask/snaps-sdk";
import { MethodNotFoundError } from "@metamask/snaps-sdk";

export const onCronjob: OnCronjobHandler = async ({ request }) => {
  switch (request.method) {
    case "execute":
      // Find out if MetaMask is locked.
      const { locked } = await snap.request({
        method: "snap_getClientStatus"
      });

      if (!locked) {
        // Do something that requires MetaMask to be unlocked, such as access encrypted state.
      }

    default:
      throw new MethodNotFoundError();
  }
};

snap_getEntropy

Gets a deterministic 256-bit entropy value, specific to the Snap and the user's account. You can use this entropy to generate a private key, or any other value that requires a high level of randomness. Other Snaps can't access this entropy, and it changes if the user's secret recovery phrase changes.

You can optionally specify a salt to generate different entropy for different purposes. Using a salt results in entropy unrelated to the entropy generated without a salt.

This value is deterministic: it's always the same for the same Snap, user account, and salt.

Parameters

An object containing:

• version - The number 1. This is reserved for future use.
• salt (optional) - An arbitrary string to be used as a salt for the entropy. This can be used to generate different entropy for different purposes.

Returns

The entropy as a hexadecimal string.

Example

Manifest file

snap.manifest.json

"initialPermissions": {
  "snap_getEntropy": {}
}

JavaScript

index.js

const entropy = await snap.request({
  method: "snap_getEntropy",
  params: {
    version: 1,
    salt: "foo", // Optional.
  },
});

// "0x..."
console.log(entropy);

snap_getFile

Gets a static file's content in UTF-8, Base64, or hexadecimal. The file must be specified in the Snap's manifest file.

Parameters

An object containing:

• path - The path to the file, relative to the Snap's package directory (that is, one level above src).
• encoding (optional) - One of utf8, base64, or hex. The default is base64.

Returns

The file content as a string in the requested encoding.

Example

Manifest file

snap.manifest.json

"source": {
  "shasum": "xxx",
  "location": {
    // ...
  },
  "files": [
    "./files/myfile.bin"
  ]
}

JavaScript

index.js

const contents = await snap.request({
  method: "snap_getFile",
  params: {
    path: "./files/myfile.bin",
    encoding: "hex",
  },
});

// "0x..."
console.log(contents);

snap_getLocale

Gets the user's locale setting. You can use this method to localize text in your snap.

Returns

The user's locale setting as a language code.

Example

index.js

import { panel, text } from "@metamask/snaps-sdk";

const locale = await snap.request({ method: "snap_getLocale" });

let greeting = "Hello";
if(locale === "es") {
  greeting = "Hola";
}

await snap.request({
  method: "snap_dialog",
  params: {
    type: "alert",
    content: panel([
      text(greeting),
    ]),
  },
});

snap_manageAccounts

Manages account management Snap accounts. This method is organized into multiple sub-methods which each take their own parameters:

• createAccount
• updateAccount
• deleteAccount
• listAccounts
• submitResponse

createAccount

Creates a new Snap account.

note

The Snap is responsible for maintaining its own record of accounts. This can be done using snap_manageState.

Parameters

account - An account object.

Returns

null

Example

index.ts

import { Keyring, KeyringAccount } from "@metamask/keyring-api";

class MyKeyring implements Keyring {
  // Other methods.

  async createAccount(
    name: string,
    options: Record<string, Json> | null = null,
  ): Promise<KeyringAccount> {

    const account: KeyringAccount = {
      id: uuid(),
      name,
      options,
      address,
      supportedMethods: [
        "eth_sendTransaction",
        "eth_sign",
        "eth_signTransaction",
        "eth_signTypedData_v1",
        "eth_signTypedData_v2",
        "eth_signTypedData_v3",
        "eth_signTypedData_v4",
        "eth_signTypedData",
        "personal_sign",
      ],
      type: "eip155:eoa",
    };

    // Store the account in state.

    await snap.request({
      method: "snap_manageAccounts",
      params: {
        method: "createAccount",
        params: { account },
      },
    });

    return account;
  }
}

updateAccount

Updates an existing Snap account.

note

The Snap is responsible for maintaining its own record of accounts. This can be done using snap_manageState.

Parameters

account - An account object.

Returns

null

Example

index.ts

import { Keyring, KeyringAccount } from "@metamask/keyring-api";

class MyKeyring implements Keyring {
  // Other methods.

  async updateAccount(account: KeyringAccount): Promise<void> {
    // Store the new account details in state.

    await snap.request({
      method: "snap_manageAccounts",
      params: {
        method: "updateAccount",
        params: { account },
      },
    });
  }
}

deleteAccount

Deletes a Snap account.

note

The Snap is responsible for maintaining its own record of accounts. This can be done using snap_manageState.

Parameters

id - The ID of the account to be deleted.

Returns

null

Example

index.ts

import { Keyring } from "@metamask/keyring-api";

class MyKeyring implements Keyring {
  // Other methods.

  async deleteAccount(id: string): Promise<void> {
    // Delete the account from state.

    await snap.request({
      method: "snap_manageAccounts",
      params: {
        method: "deleteAccount",
        params: { id },
      },
    });
  }
}

listAccounts

Lists the calling Snap's accounts that are known to MetaMask. This method does not call back to the Snap. Instead, the Snap can use it to check whether there's a discrepancy between the Snap's internal state of accounts and the state known to MetaMask.

Returns

An array of account objects.

Example

index.ts

import { Keyring, KeyringAccount } from "@metamask/keyring-api";

class MyKeyring implements Keyring {
  // Other methods.

  async checkIfAccountsInSync(): Promise<boolean> {

    const knownAccounts: KeyringAccount[] = /* Grab accounts from Snap state. */;

    const listedAccounts: KeyringAccount[] = await snap.request({
      method: "snap_manageAccounts",
      params: {
        method: "listAccounts",
      },
    });

    // Compare the arrays and return the response.
  }
}

submitResponse

Finalizes a signing request. This is usually called as part of the keyring_approveRequest method.

Parameters

• id - The ID of the request to finalize.
• result - The result that should be returned to the original JSON-RPC caller.

Returns

null

Example

index.ts

import { Keyring } from "@metamask/keyring-api";
import { Json } from "@metamask/utils";

class MyKeyring implements Keyring {
  // Other methods.

  async approveRequest(id: string, result?: Json): Promise<void> {
    // Do any Snap-side logic to finish approving the request.

    await snap.request({
      method: "snap_manageAccounts",
      params: {
        method: "submitResponse",
        params: { id, result },
      },
    });
  }
}

snap_manageState

Allows the Snap to persist up to 100 MB of data to disk and retrieve it at will. By default, the data is automatically encrypted using a Snap-specific key and automatically decrypted when retrieved. You can set encrypted to false to use unencrypted storage.

Parameters

An object containing:

• operation - The state operation to perform ("clear", "get", or "update").
• newState - The value to update state with if the operation is "update", and nothing otherwise.
• encrypted (optional) - Indicates whether the Snap will encrypt the data. The default is true.

Returns

The value stored in state if the operation is get, and null otherwise.

Example

index.js

// Persist some data.
await snap.request({
  method: "snap_manageState",
  params: { 
    operation: "update",
    newState: { hello: "world" },
  },
});

// At a later time, get the stored data.
const persistedData = await snap.request({
  method: "snap_manageState",
  params: { operation: "get" },
});

console.log(persistedData);
// { hello: "world" }

// If there's no need to store data anymore, clear it out.
await snap.request({
  method: "snap_manageState",
  params: { 
    operation: "clear",
  },
});

snap_notify

Displays a notification in MetaMask or natively in the OS. Snaps can trigger a short notification text for actionable or time sensitive information.

Parameters

An object containing the contents of the notification:

• type - The notification type ("inApp" or "native"). We recommend using type: "inApp" because there's no guarantee that native notifications are displayed to the user.
• message - A message to show in the notification.

Example

index.js

await snap.request({
  method: "snap_notify",
  params: {
    type: "inApp",
    message: "Hello, world!",
  },
});

Interactive UI methods

The following methods are used in interactive UI. These methods do not require requesting permission in the Snap manifest file.

snap_createInterface

Creates an interactive interface for use in interactive UI.

Parameters

An object containing:

• ui - The custom UI to create.

Returns

The interface's ID to be used in snap_dialog, returned from onTransaction or onHomePage.

Example

index.js

const interfaceId = await snap.request({
  method: "snap_createInterface",
  params: {
    ui: panel([
      heading("Interactive interface"),
      button({
        value: "Click me",
        name: "interactive-button",
      }),
    ])
  },
});

await snap.request({
  method: "snap_dialog",
  params: {
    type: "Alert",
    id: interfaceId
  }
});

snap_getInterfaceState

Gets the state of an interactive interface by its ID. For use in interactive UI.

Parameters

• id - The ID of the interface.

Returns

An object where each top-level property can be one of the following:

• The name of an input with its current value.
• The name of a form, with a nested object containing the current values of all inputs in the form.

Example

index.js

const interfaceId = await snap.request({
  method: "snap_createInterface",
  params: {
    ui: panel([
      heading("Interactive UI Example Snap"),
      // A top-level input.
      input({
        name: "top-level-input",
        placeholder: "Enter something",
      }),
      // A top-level form...
      form({
        name: "example-form",
        children: [
          // ...with a nested input.
          input({
            name: "nested-input",
            placeholder: "Enter something",
          }),
          button("Submit", ButtonType.Submit, "submit"),
        ],
      }),
    ]),
  },
});

const state = await snap.request({
  method: "snap_getInterfaceState",
  params: {
    id: interfaceId,
  },
});

console.log(state);
/*
{
  "top-level-input": "What the user typed in that field",
  "example-form": {
    "nested-input": "What the user typed in that field"
  }
}
*/

snap_updateInterface

Updates an interactive interface. For use in interactive UI.

Parameters

An object containing:

• id - The ID of the interface to be updated, usually received in the onUserInput entry point.
• ui - The custom UI to create.

Example

index.js

export function onUserInput({ id, event }) {
  console.log("Received input event", event);

  await snap.request({
    method: "snap_updateInterface",
    params: {
      id,
      ui: panel([
        heading("New interface"),
      ]),
    },
  });
};