Developer

Binance Chain Wallet injects a global API into websites visited by its users at window.BinanceChain.

This API specification borrows heavily from API MetaMask provided, considering the massive adoption. So Web3 site developers can easily connect their dApps with the Binance Chain Wallet. The APIs allow websites to request users' Binance Smart Chain addresses, read data from the blockchain the user is connected to, and prompt the users to sign messages and transactions.

The presence of the provider object window.BinanceChain indicates a Binance Chain/Binance Smart Chain user.

The API this extension wallet provides includes API specified by EIP-1193 and API defined by MetaMask (including some massively relied legacy ones).

Development Progress

Currently (version 1.112.8) as Binance Chain Wallet natively supports Binance Chain, we are planning to open a series of APIs for dApp developers to interact with Binance Chain. At the end of the day, most APIs available in Binance Chain javascript sdk would be available.

Currently, only the following is supported: * transfer

Difference with MetaMask

Warning

Please read through this section if you are a web3 developer who has integrated with MetaMask and interested in integrating with Binance Chain Wallet.

Inpage injected object

The biggest difference between Binance Chain Wallet and MetaMask is we inject BinanceChain rather than ethereum (or web3) to the web page. So user could keep two extensions at the same time.

BinanceChain.request({method: "eth_sign", params: ["address", "message"])

We haven't supported the full complex signing data APIs MetaMask provided, while we only provide standard eth_sign JSON-RPC call.

The message item in params for this request on MetaMask has to be hex-encoded keccak256 hash (otherwise the API would silent failure for dapp https://www.reddit.com/r/Metamask/comments/9wp7kj/eth_sign_not_working/). In contrast, web3 developers could pass any message in plaintext to this method, and our UI would render it as it is to the wallet users.

BinanceChain.request({method: "eth_accounts"})

When this API is invoked without the user's approval, MetaMask would return an empty array.

In contrast, we would ask the user to unlock his wallet and return the address user connected to.

Upcoming Breaking Changes

Warning

Important Information

On November 16, 2020, MetaMask is making changes to their provider API that will be breaking for some web3 sites. These changes are upcoming, but you can prepare for them today. Follow this GitHub issue for updates.

In this implementation, some APIs will be supported as Legacy API (For example we will still implement the chainIdChanged on BinanceChain object until MetaMask formally deprecates it).

Basic Usage

For any non-trivial Binance Smart Chain web application — a.k.a. web3 site — to work, you will have to:

  1. Detect the Binance Smart Chain provider (window.BinanceChain)
  2. Detect which Binance Smart Chain network the user is connected to
  3. Get the user's Binance Smart Chain account(s)

You can learn how to accomplish the 2 and 3 from above list by reviewing the snippet in the Using the Provider section.

The provider API is all you need to create a full-featured web3 application.

That said, many developers use a convenience library, such as ethers and web3.js, instead of using the provider directly. If you need higher-level abstractions than those provided by this API, we recommend that you use a convenience library.

Today, many dApps are built on top of the higher-level API provided by web3-react or use-wallet (which builds on top of web3-react).

  • web3-react

We made a tiny lib bsc-connector that implements the AbstractConnector interface of web3-react library. You can add this to your project in parallel with injected-connector by: yarn add @binance-chain/web3-connector or npm i @binance-chain/bsc-connector.

import { BscConnector } from '@binance-chain/bsc-connector'

export const bsc = new BscConnector({
  supportedChainIds: [56, 97] // later on 1 ethereum mainnet and 3 ethereum ropsten will be supported
})

// invoke method on bsc e.g.
await bsc.activate();
await bsc.getAccount();
await bsc.getChainId();
  • use-wallet

There is an example in use-wallet origin repo shows how to 'inject' a customized web3-react connector to UseWalletProvider:

function App() {
  const { account, connect, reset, status } = useWallet()
  return (
    <div>
      <h1>Binance Chain Connector</h1>
      {status === 'disconnected' ? (
        <button onClick={() => connect('bsc')}>Connect</button>
      ) : (
        <button onClick={() => reset()}>Disconnect</button>
      )}
      {account && <p>Connected as {account}</p>}
    </div>
  )
}

render(
  <UseWalletProvider
    connectors={{
      bsc: {
        web3ReactConnector() {
          return new BscConnector({ supportedChainIds: [56, 97] })
        },
        handleActivationError(err) {
          if (err instanceof UserRejectedRequestError) {
            return new ConnectionRejectedError()
          }
        },
      },
    }}
  >
  <App />
  </UseWalletProvider>,
  document.getElementById('root')
)

Chain IDs

Warning

At the moment, the BinanceChain.chainId property and the chainChanged event should be preferred over the eth_chainId RPC method.

Their chain ID values are correctly formatted, per the table below.

eth_chainId returns an incorrectly formatted (0-padded) chain ID for the chains in the table below, e.g. 0x01 instead of 0x1. See the Upcoming Breaking Changes section for details on when the eth_chainId RPC method will be fixed.

Custom RPC endpoints are not affected; they always return the chain ID specified by the user.

These are the IDs of the Binance Smart chains that Binance Chain Wallet supports by default.

Hex Decimal Network
0x38 56 Binance Smart Chain Main Network (bsc-mainnet)
0x61 97 Binance Smart Chain Test Network (bsc-testnet)

This API can also return chain ids of Binance Chains if users switch to them. The possible return value would be: | Chain Id | Network | | -------------------- | ---------------------------------------- | | Binance-Chain-Tigris | Binance Chain Main Network (bbc-mainnet) | | Binance-Chain-Ganges | Binance Chain Test Network (bbc-testnet) |

Properties

BinanceChain.chainId

Warning

The value of this property can change at any time, and should not be exclusively relied upon. See the chainChanged event for details.

NOTE: See the Chain IDs section for important information about the Binance Chain Wallet provider's chain IDs.

A hexadecimal string representing the current chain ID.

BinanceChain.autoRefreshOnNetworkChange

As the consumer of this API, it is your responsibility to handle chain changes using the chainChanged event. We recommend reloading the page on chainChange unless you have a good reason not to.

Please refer to MetaMask Doc, the only difference is we injected a different object.

To disable this behavior, set this property to false immediately after detecting the provider:

BinanceChain.autoRefreshOnNetworkChange = false;

Methods

BinanceChain.isConnected()

Please refer to MetaMask Doc, the only difference is we injected a different object.

BinanceChain.isConnected(): boolean;

BinanceChain.request(args)

Please refer to MetaMask Doc, the only difference is we injected a different object.

We use this method to wrap an RPC API, Please see the Ethereum wiki.

Important methods from this API include:

interface RequestArguments {
  method: string;
  params?: unknown[] | object;
}

BinanceChain.request(args: RequestArguments): Promise<unknown>;

Example

The code snippet below is as same as MetaMask's example, the only difference is we injected a different object.

params: [
  {
    from: '0xb60e8dd61c5d32be8058bb8eb970870f07233155',
    to: '0xd46e8dd67c5d32be8058bb8eb970870f07244567',
    gas: '0x76c0', // 30400
    gasPrice: '0x9184e72a000', // 10000000000000
    value: '0x9184e72a', // 2441406250
    data:
      '0xd46e8dd67c5d32be8d46e8dd67c5d32be8058bb8eb970870f072445675058bb8eb970870f072445675',
  },
];

BinanceChain
  .request({
    method: 'eth_sendTransaction',
    params,
  })
  .then((result) => {
    // The result varies by by RPC method.
    // For example, this method will return a transaction hash hexadecimal string on success.
  })
  .catch((error) => {
    // If the request fails, the Promise will reject with an error.
  });

BinanceChain.bnbSign(address: string, message: string): Promise<{publicKey: string, signature: string}>

We prepared an example for this API, please check out: https://github.com/binance-chain/js-eth-personal-sign-examples for more detail

Like eth_sign enable dapp to verify a user has control over an ethereum address by signing an arbitrary message. We provide this method for dapp developers to request the signature of arbitrary messages for Binance Chain (BC) and Binance Smart Chain (BSC).

If address parameter is a binance chain address (start with bnb or tbnb), we will simply calculate sha256 hash of the message and let user sign the hash with his binance chain address' private key. Note: Binance Chain uses the same elliptic curve (secp256k1) as Ethereum.

If address parameter is a binance smart chain address (start with 0x), the message would be hashed in the same way with eth_sign.

The returned publicKey would be a compressed encoded format (a hex string encoded 33 bytes starting with "0x02", "0x03") for Binance Chain. And uncompressed encoded format (a hex string encoded 65 bytes starting with "0x04").

The returned signature would be bytes encoded in hex string starting with 0x. For BinanceChain, its r,s catenated 64 bytes in total. For Binance Smart Chain, like eth_sign, its r, s catenated 64 bytes and a recover byte in the end.

Warning

DApp developers should verify whether the returned public key can be converted into the address user claimed in addition to an ECDSA signature verification. Because any plugin can inject the same object BinanceChain as Binance Chain Wallet.

BinanceChain.switchNetwork(networkId: string): Promise<{networkId: string}>

As Binance Chain Wallet natively supports Binance Chain and Binance Smart Chain which are heterogeneous blockchains run in parallel. APIs would be different in any situation. (We would open APIs for Binance Chain very soon).

Developers could judge which network is selected by user currently via BinanceChain.chainId or listening to the chainChanged event via BinanceChain.on('chainChanged', callback).

To request for network switching, developers could invoke this API with bbc-mainnet (Binance Chain Main Network), bsc-mainnet (Binance Smart Chain Main Network), bbc-testnet (Binance Chain Test Network), bsc-testnet (Binance Smart Chain Test Network) to prompt user to agree on network switching.

BinanceChain.requestAccounts()

Request all accounts maintained by this extension.

The id in response would be used as accountId for the APIs for Binance Chain.

This method would return an array of Account:

{
  addresses: [{address: string, type: string}],
  icon: string,
  id: string,
  name: string
}

For example:

[
    {
        "id":"fba0b0ce46c7f79cd7cd91cdd732b6c699440acf8c539d7e7d753d38c9deea544230e51899d5d9841b8698b74a3c77b79e70d686c76cb35dca9cac0e615628ed",
        "name":"Account 1",
        "icon":"data:image/svg+xml;base64,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",
        "addresses":[
            {
                "type":"bbc-testnet",
                "address":"tbnb1akt8vgstdaz8pax5zgykzee5u9kamjdkkcf2dw"
            },
            {
                "type":"bbc-mainnet",
                "address":"bnb1akt8vgstdaz8pax5zgykzee5u9kamjdkcdqwdl"
            },
            {
                "type":"eth",
                "address":"0x43364696e478E344E95831CE8427623202e5CBFb"
            }
        ]
    }
]

BinanceChain.transfer({fromAddress:string, toAddress:string, asset:string, amount:number, memo?: string, sequence?: number, accountId:string, networkId:string})>

Transfer certain amount of asset (BNB or BEP2) on Binance Chain.

accountId could be retrieved from the BinanceChain.requestAccounts API (id field of each account)

networkId could be bbc-mainnet or bbc-testnet

For example:

  1. This will ask the user's approval for transferring 1 BNB to himself. BinanceChain.transfer({fromAddress:"tbnb1sndxdzsg42jg8lc0hehx8dzzpyfxrvq937mt0w", toAddress:"tbnb1sndxdzsg42jg8lc0hehx8dzzpyfxrvq937mt0w", asset:"BNB", amount:1, accountId:"fba0b0ce46c7f79cd7cd91cdd732b6c699440acf8c539d7e7d753d38c9deea544230e51899d5d9841b8698b74a3c77b79e70d686c76cb35dca9cac0e615628ed", networkId:"bbc-testnet"})

  2. This will ask the user's approval for transferring 1 BUSD to himself. BinanceChain.transfer({fromAddress:"tbnb1sndxdzsg42jg8lc0hehx8dzzpyfxrvq937mt0w", toAddress:"tbnb1sndxdzsg42jg8lc0hehx8dzzpyfxrvq937mt0w", asset:"BUSD-BAF", amount:1, accountId:"fba0b0ce46c7f79cd7cd91cdd732b6c699440acf8c539d7e7d753d38c9deea544230e51899d5d9841b8698b74a3c77b79e70d686c76cb35dca9cac0e615628ed", networkId:"bbc-testnet"})

Events

Please refer to MetaMask Doc, the only difference is we injected a different object.

BinanceChain.on('accountsChanged', (accounts) => {
  // Handle the new accounts, or lack thereof.
  // "accounts" will always be an array, but it can be empty.
});

BinanceChain.on('chainChanged', (chainId) => {
  // Handle the new chain.
  // Correctly handling chain changes can be complicated.
  // We recommend reloading the page unless you have a very good reason not to.
  window.location.reload();
});

connect

Please refer to MetaMask Doc, the only difference is we injected a different object.

interface ConnectInfo {
  chainId: string;
}

BinanceChain.on('connect', handler: (connectInfo: ConnectInfo) => void);

disconnect

Please refer to MetaMask Doc, the only difference is we injected a different object.

BinanceChain.on('disconnect', handler: (error: ProviderRpcError) => void);

accountsChanged

Please refer to MetaMask Doc, the only difference is we injected a different object.

BinanceChain.on('accountsChanged', handler: (accounts: Array<string>) => void);

chainChanged

Please refer to MetaMask Doc, the only difference is we injected a different object.

BinanceChain.on('chainChanged', handler: (chainId: string) => void);
BinanceChain.on('chainChanged', (_chainId) => window.location.reload());

message

Please refer to MetaMask Doc, the only difference is we injected a different object.

interface ProviderMessage {
  type: string;
  data: unknown;
}

BinanceChain.on('message', handler: (message: ProviderMessage) => void);

Errors

Please refer to MetaMask Doc, the only difference is we injected a different object.

Using the Provider

This snippet explains how to accomplish the three most common requirements for web3 sites:

  • Detect which BinanceChain network the user is connected to
  • Get the user's BinanceChain account(s)
/**********************************************************/
/* Handle chain (network) and chainChanged (per EIP-1193) */
/**********************************************************/

// Normally, we would recommend the 'eth_chainId' RPC method, but it currently
// returns incorrectly formatted chain ID values.
let currentChainId = BinanceChain.chainId;

BinanceChain.on('chainChanged', handleChainChanged);

function handleChainChanged(_chainId) {
  // We recommend reloading the page, unless you must do otherwise
  window.location.reload();
}

/***********************************************************/
/* Handle user accounts and accountsChanged (per EIP-1193) */
/***********************************************************/

let currentAccount = null;
BinanceChain
  .request({ method: 'eth_accounts' })
  .then(handleAccountsChanged)
  .catch((err) => {
    // Some unexpected error.
    // For backwards compatibility reasons, if no accounts are available,
    // eth_accounts will return an empty array.
    console.error(err);
  });

// Note that this event is emitted on page load.
// If the array of accounts is non-empty, you're already
// connected.
BinanceChain.on('accountsChanged', handleAccountsChanged);

// For now, 'eth_accounts' will continue to always return an array
function handleAccountsChanged(accounts) {
  if (accounts.length === 0) {
    // Binance Chain Wallet is locked or the user has not connected any accounts
    console.log('Please connect to Binance Chain Wallet.');
  } else if (accounts[0] !== currentAccount) {
    currentAccount = accounts[0];
    // Do any other work!
  }
}

/*********************************************/
/* Access the user's accounts (per EIP-1102) */
/*********************************************/

// You should only attempt to request the user's accounts in response to user
// interaction, such as a button click.
// Otherwise, you popup-spam the user like it's 1999.
// If you fail to retrieve the user's account(s), you should encourage the user
// to initiate the attempt.
document.getElementById('connectButton', connect);

function connect() {
  BinanceChain
    .request({ method: 'eth_requestAccounts' })
    .then(handleAccountsChanged)
    .catch((err) => {
      if (err.code === 4001) {
        // EIP-1193 userRejectedRequest error
        // If this happens, the user rejected the connection request.
        console.log('Please connect to MetaMask.');
      } else {
        console.error(err);
      }
    });
}

Legacy API

Warning

You should never rely on any of these methods, properties, or events in practice.

This section documents MetaMask's legacy provider API.

To be compatible with existing dApps that support MetaMask, Binance Chain Wallet implements them as well, but please don't rely on them. We may deprecate them soon in the future.

Legacy Properties

BinanceChain.networkVersion (DEPRECATED)

Please refer to MetaMask Doc, the only difference is we injected a different object.

BinanceChain.selectedAddress (DEPRECATED)

Please refer to MetaMask Doc, the only difference is we injected a different object.

Legacy Methods

BinanceChain.enable() (DEPRECATED)

Please refer to MetaMask Doc, the only difference is we injected a different object.

BinanceChain.sendAsync() (DEPRECATED)

Please refer to MetaMask Doc, the only difference is we injected a different object.

interface JsonRpcRequest {
  id: string | undefined;
  jsonrpc: '2.0';
  method: string;
  params?: Array<any>;
}

interface JsonRpcResponse {
  id: string | undefined;
  jsonrpc: '2.0';
  method: string;
  result?: unknown;
  error?: Error;
}

type JsonRpcCallback = (error: Error, response: JsonRpcResponse) => unknown;

BinanceChain.sendAsync(payload: JsonRpcRequest, callback: JsonRpcCallback): void;

BinanceChain.send() (DEPRECATED)

Please refer to MetaMask Doc, the only difference is we injected a different object.

BinanceChain.send(
  methodOrPayload: string | JsonRpcRequest,
  paramsOrCallback: Array<unknown> | JsonRpcCallback,
): Promise<JsonRpcResponse> | void;

This method behaves unpredictably and should be avoided at all costs. It is essentially an overloaded version of BinanceChain.sendAsync().

BinanceChain.send() can be called in three different ways:

// 1.
BinanceChain.send(payload: JsonRpcRequest, callback: JsonRpcCallback): void;

// 2.
BinanceChain.send(method: string, params?: Array<unknown>): Promise<JsonRpcResponse>;

// 3.
BinanceChain.send(payload: JsonRpcRequest): unknown;

You can think of these signatures as follows:

  1. This signature is exactly like BinanceChain.sendAsync()

  2. This signature is like an async BinanceChain.sendAsync() with method and params as arguments, instead of a JSON-RPC payload and callback

  3. This signature enables you to call the following RPC methods synchronously:

  4. eth_accounts

  5. eth_coinbase
  6. eth_uninstallFilter
  7. net_version

Legacy Events

close (DEPRECATED)

Please refer to MetaMask Doc, the only difference is we injected a different object.

BinanceChain.on('close', handler: (error: Error) => void);

chainIdChanged (DEPRECATED)

Please refer to MetaMask Doc, the only difference is we injected a different object.

BinanceChain.on('chainChanged', handler: (chainId: string) => void);

networkChanged (DEPRECATED)

Please refer to MetaMask Doc, the only difference is we injected a different object.

BinanceChain.on('networkChanged', handler: (networkId: string) => void);

notification (DEPRECATED)

Please refer to MetaMask Doc, the only difference is we injected a different object.

BinanceChain.on('notification', handler: (payload: any) => void);