EIPs/EIPS/eip-1193.md

---
eip: 1193
title: Ethereum Provider JavaScript API
author: Ryan Ghods (@ryanio), Marc Garreau (@marcgarreau)
discussions-to: https://ethereum-magicians.org/t/eip-1193-ethereum-provider/640
status: Draft
type: Standards Track
category: Interface
created: 2018-06-30
requires: 1102
---

## Summary

This proposal formalizes an Ethereum Provider JavaScript API.

The provider is designed to be minimal, containing 3 methods: `send`, `subscribe`, and `unsubscribe`. It emits 4 types of events: `connect`, `close`, `networkChanged`, and `accountsChanged`.

## API

### Send

```js
ethereum.send(method: String, params?: Array<any>): Promise<any>;
```

Promise resolves with `result` or rejects with `Error`.

See the [available methods](https://github.com/ethereum/wiki/wiki/JSON-RPC#json-rpc-methods).

### Subscriptions

#### Subscribe

```js
ethereum.subscribe(subscriptionType: String, params?: Array<any>): Promise<any>;
```

Promise resolves with `subscriptionId: String` or rejects with `Error`.

See the [types of subscriptions](https://github.com/ethereum/go-ethereum/wiki/RPC-PUB-SUB#supported-subscriptions).

Results emit on `subscriptionId` using [EventEmitter](https://nodejs.org/api/events.html). Attach listeners with:

```js
ethereum.on(subscriptionId, listener: (result: any) => void): this;
```

The event emits with `result`, the subscription `result` or an `Error` object.

#### Unsubscribe

```js
ethereum.unsubscribe(subscriptionId: String): Promise<Boolean|Error>;
```

Promise resolves with `success: Boolean` or rejects with `Error`.

All [EventEmitter](https://nodejs.org/api/events.html) listeners on `subscriptionId` will also be removed.

### Events

Events are emitted using [EventEmitter](https://nodejs.org/api/events.html).

#### connect

The provider emits `connect` on connect to a network.

```js
ethereum.on('connect', listener: () => void): this;
```

You can detect which network by sending `net_version`:

```js
const network = await ethereum.send('net_version');
> '1'
```

#### close

The provider emits `close` on disconnect from a network.

```js
ethereum.on('close', listener: (code: Number, reason: String) => void): this;
```

The event emits with `code` and `reason`. The code follows the table of [`CloseEvent` status codes](https://developer.mozilla.org/en-US/docs/Web/API/CloseEvent#Status_codes).

#### networkChanged

The provider emits `networkChanged` on connect to a new network.

```js
ethereum.on('networkChanged', listener: (networkId: String) => void): this;
```

The event emits with `networkId`, the new network returned from `net_version`.

#### accountsChanged

The provider emits `accountsChanged` if the accounts returned from the provider (`eth_accounts`) changes.

```js
ethereum.on('accountsChanged', listener: (accounts: Array<String>) => void): this;
```

The event emits with `accounts`, an array of the accounts' public keys.

### Constructor

```js
ethereum.constructor.name;
> 'EthereumProvider'
```

## Examples

```js
// Request Ethereum Provider (EIP 1102)
window.addEventListener('message', event => {
  if (event.data && event.data.type === 'ETHEREUM_PROVIDER_SUCCESS') {
    start(window.ethereum);
  }
});
window.postMessage({ type: 'ETHEREUM_PROVIDER_REQUEST' }, this.origin);

function start(ethereum) {
  // A) Primary use case - set provider in web3.js
  web3.setProvider(ethereum);

  // B) Secondary use case - use provider object directly
  // Example: Log accounts
  ethereum
    .send('eth_accounts')
    .then(accounts => {
      console.log(`Accounts:\n${accounts.join('\n')}`);
    })
    .catch(error => {
      console.error(
        `Error fetching accounts: ${error.message}.
         Code: ${error.code}. Data: ${error.data}`
      );
    });

  // Example: Log last block
  ethereum
    .send('eth_getBlockByNumber', ['latest', 'true'])
    .then(block => {
      console.log(`Block ${block.number}:\n${block}`);
    })
    .catch(error => {
      console.error(
        `Error fetching last block: ${error.message}.
         Code: ${error.code}. Data: ${error.data}`
      );
    });

  // Example: Log new blocks
  let subId;
  ethereum
    .subscribe('newHeads')
    .then(subscriptionId => {
      subId = subscriptionId;
      ethereum.on(subscriptionId, block => {
        if (result instanceOf Error) {
          const error = result;
          console.error(
            `Error from newHeads subscription: ${error.message}.
             Code: ${error.code}. Data: ${error.data}`
          );
        } else {
          console.log(`New block ${block.number}:\n${block}`);
        }
      });
    })
    .catch(error => {
      console.error(
        `Error making newHeads subscription: ${error.message}.
         Code: ${error.code}. Data: ${error.data}`
       );
    });
  // to unsubscribe
  ethereum
    .unsubscribe(subId)
    .then(result => {
      console.log(`Unsubscribed newHeads subscription ${subscriptionId}`);
    })
    .catch(error => {
      console.error(
        `Error unsubscribing newHeads subscription: ${error.message}.
         Code: ${error.code}. Data: ${error.data}`
      );
    });

  // Example: Log when accounts change
  const logAccounts = accounts => {
    console.log(`Accounts:\n${accounts.join('\n')}`);
  };
  ethereum.on('accountsChanged', logAccounts);
  // to unsubscribe
  ethereum.removeListener('accountsChanged', logAccounts);

  // Example: Log if connection ends
  ethereum.on('close', (code, reason) => {
    console.log(
      `Ethereum provider connection closed: ${reason}. Code: ${code}`
    );
  });
}
```

## Specification

### Send

The `send` method **MUST** send a properly formatted [JSON-RPC request](https://www.jsonrpc.org/specification#request_object).

If the Ethereum JSON-RPC API returns a response object with no error, then the Promise **MUST** resolve with the `response.result` object untouched by the implementing Ethereum Provider.

If the Ethereum JSON-RPC API returns response object that contains an error property then the Promise **MUST** be rejected with an Error object containing the `response.error.message` as the Error message, `response.error.code` as a code property on the error and `response.error.data` as a data property on the error.

If an error occurs during processing, such as an HTTP error or internal parsing error then the Promise **MUST** be rejected with an Error object containing a human readable string message describing the error and **SHOULD** populate the `code` and `data` properties on the error object with additional error details.

If the implementing Ethereum Provider is not talking to an external Ethereum JSON-RPC API provider then it **MUST** resolve with an object that matches the JSON-RPC API object as specified in the [Ethereum JSON-RPC documentation](https://github.com/ethereum/wiki/wiki/JSON-RPC). In case of an error, ensure that the Promise is rejected with an Error that matches the above shape.

### Subscriptions

The `subscribe` method **MUST** send a properly formatted [JSON-RPC request](https://www.jsonrpc.org/specification#request_object) with method `eth_subscribe` and params `[subscriptionType: String, {...params: Array<any>}]` and **MUST** return a Promise that resolves with `subscriptionId: String` or rejected with an Error object containing a human readable string message describing the error and **SHOULD** populate the `code` and `data` properties on the error object with additional error details.

The `unsubscribe` method **MUST** send a properly formatted [JSON-RPC request](https://www.jsonrpc.org/specification#request_object) with method `eth_unsubscribe` and params `[subscriptionId: String]` and **MUST** return a Promise that resolves with `result: Boolean` or rejected with an Error object containing a human readable string message describing the error and **SHOULD** populate the `code` and `data` properties on the error object with additional error details.

If the `unsubscribe` method returns successfully with a `True` result, the implementing provider **MUST** remove all listeners on the `subscriptionId` using `ethereum.removeAllListeners(subscriptionId);`.

If an error occurs during processing of the subscription, such as an HTTP error or internal parsing error then the Promise **MUST** return with an Error object containing a human readable string message describing the error and **SHOULD** populate the `code` and `data` properties on the error object with additional error details.

The implementing Ethereum Provider **MUST** emit every subscription response `result` with the eventName `subscriptionId`.

If an error occurs or the network changes during the listening of the subscription, the Ethereum Provider **MUST** emit an Error object to the eventName `subscriptionId` containing a human readable string message describing the error and **SHOULD** populate the `code` and `data` properties on the error object with additional error details.

If the implementing provider does not support subscriptions, then it **MUST** leave the `subscribe` and `unsubscribe` methods undefined.

### Events

If the network connects, the Ethereum Provider **MUST** emit an event named `connect`.

If the network connection closes, the Ethereum Provider **MUST** emit an event named `close` with args `code: Number, reason: String` using the [status codes for `CloseEvent`](https://developer.mozilla.org/en-US/docs/Web/API/CloseEvent#Status_codes) and a short human readable reason.

If the network the Ethereum Provider is connected to changes, the Ethereum Provider **MUST** emit an event named `networkChanged` with args `networkId: String` containing the ID of the new network (using the Ethereum JSON-RPC call `net_version`).

If the accounts connected to the Ethereum Provider change, the Ethereum Provider **MUST** send an event with the name `accountsChanged` with args `accounts: Array<String>` containing the accounts' public key(s).

### Class

The name of the constructor of the Ethereum Provider **MUST** be `EthereumProvider`.

## Copyright

Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).