Provider API

OneKey Browser Extension injects a global API into websites visited by its users at window.$onekey.ethereum. This API allows websites to request users' Ethereum accounts, read data from blockchains the user is connected to, and suggest that the user sign messages and transactions. The presence of the provider object indicates an Ethereum user.

We recommend using typeof window !== 'undefined' && window.$onekey.ethereum to detect our provider in browser.

The Ethereum JavaScript provider API is specified by EIP-1193.

if (typeof window !== 'undefined' && window.$onekey?.ethereum) {  
  // From now on, this should always be true:  
  startApp(provider); // initialize your app
} else {  
  console.log('Please install OneKey Browser Extension at!');

Basic Usage

For any non-trivial Ethereum web application — a.k.a. dapp, web3 site etc. — to work, you will have to:

  • Detect the OneKey provider (window.$onekey.ethereum)

  • Detect which Ethereum network the user is connected to

  • Get the user's Ethereum account(s)

The snippet at the top of this page is sufficient for detecting the provider. You can learn how to accomplish the other two 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, instead of using the provider directly. If you are in need of higher-level abstractions than those provided by this API, we recommend that you use a convenience library.

Chain IDs

These are the IDs of the Ethereum chains that OneKey supports by default. Visit chainlist for more.




Ethereum Main Network (Mainnet)



Binance Smart Chain (Mainnet)



Huobi Eco Chain (Mainnet)



OEC Mainnet



Matic (Polygon)



Fantom Main Network



xDai Main Network



Ropsten Testnet



kovan Testnet



Rinkeby Testnet




Note that this method has nothing to do with the user's accounts.

You may often encounter the word "connected" in reference to whether a web3 site can access the user's accounts. In the provider interface, however, "connected" and "disconnected" refer to whether the provider can make RPC requests to the current chain.

window.$onekey.ethereum.isConnected(): boolean;

Returns true if the provider is connected to the current chain, and false otherwise.

If the provider is not connected, the page will have to be reloaded in order for connection to be re-established. Please see the connect and disconnect events for more information.


interface RequestArguments {  method: string;  params?: unknown[] | object;}
window.$onekey.ethereum.request(args: RequestArguments): Promise<unknown>;

Use request to submit RPC requests to Ethereum via OneKey Browser Extension. It returns a Promise that resolves to the result of the RPC method call.

The params and return value will vary by RPC method. In practice, if a method has any params, they are almost always of type Array<any>.

If the request fails for any reason, the Promise will reject with an Ethereum RPC Error.

OneKey Browser Extension supports most standardized Ethereum RPC methods, in addition to a number of methods that may not be supported by other wallets.

See the OneKey Browser Extension RPC API documentation for details.


params: [  
        from: '0xb60e8dd61c5d32be8058bb8eb970870f0java7233155',    
        to: '0xd46e8dd67c5d32be8058bb8eb970870f07244567',    
        gas: '0x76c0', // 30400    
        gasPrice: '0x9184e72a000', // 10000000000000    
        value: '0x9184e72a', // 2441406250    
        data:      '0xd46e8dd67c5d32be8d46e8dd67c5d32be8058bb8eb970870f072445675058bb8eb970870f072445675',  
    method: 'eth_sendTransaction',    
}).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.  


The OneKey Browser Extension provider implements the Node.js EventEmitter API.

This sections details the events emitted via that API.

There are innumerable EventEmitter guides elsewhere, but you can listen for events like this:

window.$onekey.ethereum.on('accountsChanged', (accounts) => {  // Handle the new accounts, or lack thereof.  // "accounts" will always be an array, but it can be empty.});
window.$onekey.ethereum.on('chainChanged', (chainId) => {  // Handle the new chain.  // Correctly handling chain changes can be complicated.  // We recommend reloading the page unless you have good reason not to.  window.location.reload();});


interface ConnectInfo {  chainId: string;}
window.$onekey.ethereum.on('connect', handler: (connectInfo: ConnectInfo) => void);

The OneKey Browser Extension provider emits this event when it first becomes able to submit RPC requests to a chain.

We recommend using a connect event handler and the window.$onekey.ethereum.isConnected() method in order to determine when/if the provider is connected.


window.$onekey.ethereum.on('disconnect', handler: (error: ProviderRpcError) => void);

The OneKey provider emits this event if it becomes unable to submit RPC requests to any chain. In general, this will only happen due to network connectivity issues or some unforeseen error.

Once disconnect has been emitted, the provider will not accept any new requests until the connection to the chain has been re-restablished, which requires reloading the page. You can also use the window.$onekey.ethereum.isConnected() method to determine if the provider is disconnected.


window.$onekey.ethereum.on('accountsChanged', handler: (accounts: Array<string>) => void);

The OneKey provider emits this event whenever the return value of the eth_accounts RPC method changes. eth_accounts returns an array that is either empty or contains a single account address. The returned address, if any, is the address of the most recently used account that the caller is permitted to access. Callers are identified by their URL origin, which means that all sites with the same origin share the same permissions.

This means that accountsChanged will be emitted whenever the user's exposed account address changes.


We plan to allow the eth_accounts array to be able to contain multiple addresses in the near future.



See the Chain IDs section for OneKey Browser Extension's default chains and their chain IDs.

window.$onekey.ethereum.on('chainChanged', handler: (chainId: string) => void);

The OneKey Browser Extension provider emits this event when the currently connected chain changes.

All RPC requests are submitted to the currently connected chain. Therefore, it's critical to keep track of the current chain ID by listening for this event.

window.$onekey.ethereum.on('chainChanged', (_chainId) => window.location.reload());


interface ProviderMessage {  type: string;  data: unknown;}
window.$onekey.ethereum.on('message', handler: (message: ProviderMessage) => void);

The OneKey provider emits this event when it receives some message that the consumer should be notified of.

The kind of message is identified by the type string.

RPC subscription updates are a common use case for the message event.

For example, if you create a subscription using eth_subscribe, each subscription update will be emitted as a message event with a type of eth_subscription.


All errors thrown or returned by the OneKey Browser Extension provider follow this interface:

interface ProviderRpcError extends Error {  message: string;  code: number;  data?: unknown;}

The window.$onekey.ethereum.request(args) method throws errors eagerly.

You can often use the error code property to determine why the request failed.

Common codes and their meaning include:

  • 4001

    • The request was rejected by the user

  • -32602

    • The parameters were invalid

  • -32603

    • Internal error

For the complete list of errors, please see EIP-1193 and EIP-1474.

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