Snaps JSON-RPC API

Snaps communicate with MetaMask using the Snaps JSON-RPC API. These API methods allow snaps to modify the functionality of MetaMask, and websites (dapps) to install and communicate with individual snaps. Some methods are only callable by snaps, and some are only callable by websites.

Unrestricted methods

You can call unrestricted methods without requesting permission to do so.

wallet_getSnaps

Returns the IDs of the caller's permitted snaps and some relevant metadata.

This method is only callable by websites.

Returns

An object containing the requester's permitted snaps. Each snap is an object containing:

• id - The ID of the snap.
• initialPermissions - The initial permissions of the snap, which will be requested when the snap is installed.
• version - The version of the snap.
• enabled - true if the snap is enabled, false otherwise.
• blocked - true if the snap is blocked, false otherwise.

Example

JavaScript

const result = await window.ethereum.request({ method: 'wallet_getSnaps' });

console.log(result);

Result

// Example result if any snaps are permitted
{
  'npm:@metamask/example-snap': {
    version: '1.0.0',
    id: 'npm:@metamask/example-snap',
    enabled: true,
    blocked: false,
  },
}

wallet_invokeSnap

Invokes the specified JSON-RPC method of the specified snap. The snap must be installed and the caller must have the permission to communicate with the snap, or the request is rejected.

Snaps are fully responsible for implementing their JSON-RPC API. Consult the snap's documentation for available methods, their parameters, and return values.

This method is only callable by websites.

Parameters

An object containing:

• snapId - The ID of the snap to invoke.
• request - The JSON-RPC request object to send to the invoked snap.

Returns

Result of the snap method call.

Example

const result = await ethereum.request({
  method: 'wallet_invokeSnap',
  params: {
    snapId: 'npm:@metamask/example-snap',
    request: {
      method: 'hello',
    },
  },
});

console.log(result); // In this example, the result is a boolean.

wallet_requestSnaps

Requests permission for a website to communicate with the specified snaps and attempts to install them if they're not already installed. If the installation of any snap fails, returns the error that caused the failure.

You can optionally specify a SemVer range for a snap. MetaMask attempts to install a version of the snap that satisfies the requested range. If a compatible version of a snap is already installed, the request succeeds. If an incompatible version is installed, MetaMask attempts to update the snap to the latest version that satisfies the requested range. The request succeeds if the snap is successfully updated.

This method is only callable by websites.

Parameters

An object containing the snaps to request permission to communicate with.

Returns

An object mapping the IDs of installed snaps to either their metadata or an error if installation fails.

Example

JavaScript

try {
  const result = await window.ethereum.request({
    method: 'wallet_requestSnaps',
    params: {
      'npm:@metamask/example-snap': {},
      'npm:fooSnap': {
        // The optional version argument allows requesting a SemVer version
        // range, with the same semantics as npm package.json ranges.
        version: '^1.0.2',
      },
    },
  });

  console.log(result);

} catch (error) {
  console.log(error);
}

Result

{
  'npm:@metamask/example-snap': {
    version: '1.0.0',
    id: 'npm:@metamask/example-snap',
    enabled: true,
    blocked: false,
  },
  'npm:fooSnap': {
    version: '1.0.5',
    id: 'npm:fooSnap',
    enabled: true,
    blocked: false,
  },
}

Restricted methods

For restricted methods callable by snaps, a snap must request permission to call the method in the snap manifest file. For restricted methods callable by websites, a website must request permission to call the method using wallet_requestPermissions.

snap_dialog

Displays a dialog in the MetaMask UI. There are three types of dialogs with different parameters and return types:

• Alert
• Confirmation
• Prompt

This method is only callable by snaps.

Alert dialog

Displays an alert that can only be acknowledged.

Parameters

An object containing the contents of the alert dialog:

• type - The type of dialog ('Alert').
• content - The content of the alert, as a custom UI component.

Example

import { panel, text, heading } from '@metamask/snaps-ui';

await snap.request({
  method: 'snap_dialog',
  params: {
    type: 'Alert',
    content: panel([
      heading('Something happened in the system'),
      text('The thing that happened is...'),
    ]),
  },
});

// Code that should execute after the alert has been acknowledged

Confirmation dialog

Displays a confirmation that can be accepted or rejected.

Parameters

An object containing the contents of the confirmation dialog:

• type - The type of dialog ('Confirmation').
• content - The content of the confirmation, as a custom UI component.

Returns

true if the confirmation was accepted, false otherwise.

Example

import { panel, text, heading } from '@metamask/snaps-ui';

const result = await snap.request({
  method: 'snap_dialog',
  params: {
    type: 'Confirmation',
    content: panel([
      heading('Would you like to take the action?'),
      text('The action is...'),
    ]),
  },
});

if (result === true) {
  // Do the action
}

Prompt dialog

Displays a prompt where the user can enter a text response.

Parameters

An object containing the contents of the prompt dialog:

• type - The type of dialog ('Prompt').
• content - The content of the prompt, as a custom UI component.
• placeholder - Text that will be in the input field when nothing is typed.

Returns

The text entered by the user.

Example

import { panel, text, heading } from '@metamask/snaps-ui';

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.

This method is only callable by snaps.

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

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

JavaScript

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: {
    // Must be specified exactly in the manifest
    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.

This method is only callable by snaps.

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

{
  "initialPermissions": {
    "snap_getBip32PublicKey": [
      {
        "path": ["m", "44'", "3'", "0'", "0", "0"],
        "curve": "secp256k1" // Or "ed25519"
      }
    ]
  }
}

JavaScript

// 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.

This method is only callable by snaps.

Parameters

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

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

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

JavaScript

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_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.

This method is only callable by snaps.

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

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

JavaScript

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

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

snap_manageState

Allows the snap to persist up to 100 MB of data to disk and retrieve it at will. The data is automatically encrypted using a snap-specific key and automatically decrypted when retrieved.

This method is only callable by snaps.

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.

Returns

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

Example

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

// At a later time, get the data stored.
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 browser. Snaps can trigger a short notification text for actionable or time sensitive information.

This method is only callable by snaps.

Parameters

An object containing the contents of the notification:

• type - The notification type. Specify inApp to display the notification in the MetaMask UI, and native to display the notification in the browser. We recommend using inApp because there's no guarantee that native notifications are displayed to the user.
• message - A message to show in the notification.

Example

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

wallet_snap

A website must request the wallet_snap permission using wallet_requestPermissions to interact with the specified snaps.

A website can also call this method to invoke the specified JSON-RPC method of the specified snap.

This method is synonymous to wallet_invokeSnap, and is only callable by websites.

note

Most websites only make one call to wallet_requestPermissions. Consecutive calls to wallet_requestPermissions for the wallet_snap permission overwrites a website's existing permissions to interact with snaps. To deal with this, you must write custom logic to merge existing snap IDs with new ones you're requesting. Use wallet_getSnaps to get a list of a website's permitted snaps.

Parameters

When requesting this permission, specify a caveat of type snapIds. Specify each snap to request permission to interact with as an entry in the value field of the caveat. Each snap entry can include a version to install. The default is the latest version.

When calling this method, specify an object containing:

• snapId - The ID of the snap to invoke.
• request - The JSON-RPC request object to send to the invoked snap.

Returns

Result of the snap method call.

Example

wallet_requestPermissions

The following is an example of calling wallet_requestPermissions to request the wallet_snap permission:

const result = await ethereum.request({
  method: 'wallet_requestPermissions',
  params: [{
    wallet_snap: {
      caveats: [
        {
          type: 'snapIds',
          value: {
            'npm:@metamask/example-snap': { version: '1.0.0' },
            'npm:@metamask/foo-bar-snap': { version: '1.2.1' },
          }
        }
      ]
    }
  }],
});

wallet_snap

The following is an example of calling wallet_snap:

const result = await ethereum.request({
  method: 'wallet_snap',
  params: {
    snapId: 'npm:@metamask/example-snap',
    request: {
      method: 'hello',
    },
  },
});

console.log(result); // In this example, the result is a boolean.