NDK

NDK is a nostr development kit that makes the experience of building Nostr-related applications, whether they are relays, clients, or anything in between, better, more reliable and overall nicer to work with than existing solutions.

NDK Objectives

The core goal of NDK is to improve the decentralization of Nostr via intelligent conventions and data discovery features without depending on any one central point of coordination (such as large relays or centralized search providers).
NDK team aims to have new to nostr devs get set up, and reading a NIP-01 event within 10 minutes.
NDK's objective is to serve prospective, and current nostr devs as clients. If you have friction with the NDK developer experience, please open issues, and ask for help from the NDK team! Devs are encouraged to search through existing, and/or create new github issues when experiencing friction with NDK.

Installation

npm add @nostr-dev-kit/ndk

Debugging

NDK uses the debug package to assist in understanding what's happening behind the hood. If you are building a package that runs on the server define the DEBUG envionment variable like

export DEBUG='ndk:*'

or in the browser enable it by writing in the DevTools console

localStorage.debug = 'ndk:*'

Support

documentation

Features

Real-world uses of NDK

See REFERENCES.md for a list of projects using NDK to see how others are using it.

Instantiate an NDK instance

You can pass an object with several options to a newly created instance of NDK.

explicitRelayUrls – an array of relay URLs.
signer - an instance of a signer.
cacheAdapter - an instance of a Cache Adapter
debug - Debug instance to use for logging. Defaults to debug("ndk").

// Import the package
import NDK from "@nostr-dev-kit/ndk";

// Create a new NDK instance with explicit relays
const ndk = new NDK({
    explicitRelayUrls: ["wss://a.relay", "wss://another.relay"],
});

If the signer implements the getRelays() method, NDK will use the relays returned by that method as the explicit relays.

// Import the package
import NDK, { NDKNip07Signer } from "@nostr-dev-kit/ndk";

// Create a new NDK instance with just a signer (provided the signer implements the getRelays() method)
const nip07signer = new NDKNip07Signer();
const ndk = new NDK({ signer: nip07signer });

Note: In normal client use, it's best practice to instantiate NDK as a singleton class. See more below.

Connecting

After you've instatiated NDK, you need to tell it to connect before you'll be able to interact with any relays.

// Import the package
import NDK from "@nostr-dev-kit/ndk";

// Create a new NDK instance with explicit relays
const ndk = new NDK({
    explicitRelayUrls: ["wss://a.relay", "wss://another.relay"],
});
// Now connect to specified relays
await ndk.connect();

Signers

NDK uses signers optionally passed in to sign events. Note that it is possible to use NDK without signing events (e.g. to get someone's profile).

Signing adapters can be passed in when NDK is instantiated or later during runtime.

Using a NIP-07 browser extension (e.g. Alby, nos2x)

Instatiate NDK with a NIP-07 signer

// Import the package, NIP-07 signer and NDK event
import NDK, { NDKEvent, NDKNip07Signer } from "@nostr-dev-kit/ndk";

const nip07signer = new NDKNip07Signer();
const ndk = new NDK({ signer: nip07signer });

NDK can now ask for permission, via their NIP-07 extension, to...

Read the user's public key

nip07signer.user().then(async (user) => {
    if (!!user.npub) {
        console.log("Permission granted to read their public key:", user.npub);
    }
});

Sign & publish events

const ndkEvent = new NDKEvent(ndk);
ndkEvent.kind = 1;
ndkEvent.content = "Hello, world!";
ndkEvent.publish(); // This will trigger the extension to ask the user to confirm signing.

Caching

NDK provides database-agnostic caching functionality out-of-the-box to improve the performance of your application and reduce load on relays.

NDK will eventually allow you to use multiple caches simultaneously and allow for selective storage of data in the cache store that makes the most sense for your application.

Where to look is more important that long-term storage

The most important data to cache is where a user or note might be found. UX suffers profoundly when this type of data cannot be found. By design, the Nostr protocol leaves breadcrumbs of where a user or note might be found and NDK does it's best to store this data automatically and use it when you query for events.

Instantiating and using a cache adapter

const redisAdapter = new RedisAdapter(redisUrl);
const ndk = new NDK({ cacheAdapter: redisAdapter });

Groupable queries

Clients often need to load data (e.g. profile data) from individual components at once (e.g. initial page render). This typically causes multiple subscriptions to be submitted fetching the same information and causing poor performance or getting rate-limited/maxed out by relays.

NDK implements a convenient subscription model, buffered queries, where a named subscription will be created after a customizable amount of time, so that multiple components can append queries.

// Component 1
ndk.subscribe({ kinds: [0], authors: ["pubkey-1"] });

// Component 2
ndk.subscribe({ kinds: [0], authors: ["pubkey-2"] });

In this example, NDK will wait 100ms (default groupableDelay) before creating a subscription with the filter:

{kinds: [0], authors: ['pubkey-1', 'pubkey-2'] }

Intelligent relay selection

When a client submits a request through NDK, NDK will calculate which relays are most likely able to satisfy this request.

Queries submitted by the client might be broken into different queries if NDK computes different relays.

For example, say npub-A follows npub-B and npub-C. If the NDK client uses:

const ndk = new NDK({ explicitRelayUrls: ["wss://nos.lol"] });
const npubA = ndk.getUser("npub-A");
const feedEvents = await npubA.feed();

This would result in the following request:

{ "kinds": [1], "authors": ["npub-B", "npub-C"] }

But if NDK has observed that npub-B tends to write to wss://userb.xyz and npub-C tends to write to wss://userc.io, NDK will instead send the following queries.

// to npub-A's explicit relay wss://nos.lol *if* npub-B and npub-C have been seen on that relay
{ "kinds": [1], "authors": [ "npub-B", "npub-C" ] }

// to wss://userb.xyz
{ "kinds": [1], "authors": [ "npub-B" ] }

// to wss://userc.io
{ "kinds": [1], "authors": [ "npub-C" ] }

Auto-closing subscriptions

Often, clients need to fetch data but don't need to maintain an open connection to the relay. This is true of profile metadata requests especially. NDK defaults to having the closeOnEose flag set to false; if you want your subscription to close after EOSE, you should set it to true.

The closeOnEose flag will make the connection close immediately after EOSE is seen.

ndk.subscribe({ kinds: [0], authors: ["..."] }, { closeOnEose: false });

Convenience methods

NDK implements several conveience methods for common queries.

Instantiate a user by npub or hex pubkey

This is a handy method for instantiating a new NDKUser and associating the current NDK instance with that user for future calls.

const pablo = ndk.getUser({
    npub: "npub1l2vyh47mk2p0qlsku7hg0vn29faehy9hy34ygaclpn66ukqp3afqutajft",
});

const jeff = ndk.getUser({
    pubkey: "1739d937dc8c0c7370aa27585938c119e25c41f6c441a5d34c6d38503e3136ef",
});

Fetch a user's profile and publish updates

You can easily fetch a user's profile data from kind:0 events on relays. Calling .fetchProfile() will update the profile attribute on the user object instead of returning the profile directly. NDK then makes it trivial to update values and publish those updates back to relays.

const pablo = ndk.getUser({
    npub: "npub1l2vyh47mk2p0qlsku7hg0vn29faehy9hy34ygaclpn66ukqp3afqutajft",
});
await pablo.fetchProfile();

const pabloFullProfile = pablo.profile;

pablo.profile.name = "Pablo";
await pablo.publish(); // Triggers signing via signer

Finding a single event or all events matching a filter

You can fetch the first event or all events that match a given set of filters.

// Create a filter
const filter: NDKFilter = { kinds: [1], authors: [hexpubkey1, hexpubkey2] };

// Will return only the first event
event = await ndk.fetchEvent(filter);

// Will return all found events
events = await ndk.fetchEvents(filter);

Creating & publishing events

const ndk = new NDK({ explicitRelayUrls, signer });
const event = new NDKEvent(ndk);
event.kind = 1;
event.content = "PV Nostr! 🤙🏼";
await ndk.publish(event);

Reacting to an event

// Find the first event from @jack, and react/like it.
const event = await ndk.fetchEvent({ author: "jack@cashapp.com" })[0];
await event.react("🤙");

Zap an event

// Find the first event from @jack, and zap it.
const event = await ndk.fetchEvent({ author: "jack@cashapp.com" })[0];
await event.zap(1337, "Zapping your post!"); // Returns a bolt11 payment request

Architecture decisions & suggestions

Users of NDK should instantiate a single NDK instance.
That instance tracks state with all relays connected, explicit and otherwise.
All relays are tracked in a single pool that handles connection errors/reconnection logic.
RelaySets are assembled ad-hoc as needed depending on the queries set, although some RelaySets might be long-lasting, like the explicitRelayUrls specified by the user.
RelaySets are always a subset of the pool of all available relays.

Sebastix/ndk

NDK