Summary

NEP-21 proposes a common browser API for N3 dApps and external wallet providers. It lets a dApp obtain a wallet provider, inspect wallet metadata, read accounts, request signatures, invoke contracts, relay transactions, and query selected chain data.

This documentation is written for two readers:

Reader	What to look for
dApp developers	How to obtain a provider and call the standard methods.
Wallet providers	What shape the provider object, methods, events, and errors should have.

The API pages follow the general style of wallet dAPI documentation: each method has a short description, parameters, return value, possible errors, and an example where useful. The content itself follows the current NEP-21 proposal.

How dApps Get a Provider

NEP-21 providers are obtained through browser events.

Wallets announce a provider by dispatching Neo.DapiProvider.ready:

window.dispatchEvent(new CustomEvent("Neo.DapiProvider.ready", {
  detail: {
    provider,
  },
}));

dApps listen for this event and read the provider from event.detail.provider:

window.addEventListener("Neo.DapiProvider.ready", (event) => {
  const provider = (event as CustomEvent).detail.provider;
  console.log(provider.name);
});

A dApp may also request a provider by dispatching Neo.DapiProvider.request:

window.dispatchEvent(new CustomEvent("Neo.DapiProvider.request", {
  detail: {
    version: "1.0",
  },
}));

Wallets that support the requested version should respond by injecting or announcing a compatible provider.

Provider Metadata

The provider exposes wallet metadata as properties.

const info = {
  name: provider.name,
  version: provider.version,
  dapiVersion: provider.dapiVersion,
  compatibility: provider.compatibility,
  connected: provider.connected,
  network: provider.network,
  supportedNetworks: provider.supportedNetworks,
  icon: provider.icon,
  website: provider.website,
  extra: provider.extra,
};

If the provider supports NEP-21, compatibility should include "NEP-21".

Minimal dApp Example

let provider: any;

window.addEventListener("Neo.DapiProvider.ready", (event) => {
  provider = (event as CustomEvent).detail.provider;
});

window.dispatchEvent(new CustomEvent("Neo.DapiProvider.request", {
  detail: { version: "1.0" },
}));

// After a provider is available:
const accounts = await provider.getAccounts();
const count = await provider.getBlockCount();

console.log(accounts, count);

Pages

Page	Contents
API Reference	Provider discovery, properties, events, and methods.
Types and Errors	Shared TypeScript-style types and error codes.

Network Values

Network	Magic
MainNet	860833102
TestNet	894710606

Source

• NEP-21 proposal PR #145