Moderation Policies

Policies allow you to prevent spam on your relay (or in your client).

Nostrify introduces a model for writing policies and composing them in pipelines. Policies are fully configurable and it's easy to add your own or install more from anywhere on the net!

Usage

Policies inspect one event at a time, which they either accept or reject. It's up to the application to decide how to handle the result.

import { AntiDuplicationPolicy, FiltersPolicy, HellthreadPolicy, KeywordPolicy, PipePolicy, PowPolicy, RegexPolicy } from '@nostrify/policies';

const policy = new PipePolicy([
  new FiltersPolicy([{ kinds: [0, 1, 3, 5, 7, 1984, 9734, 9735, 10002] }]),
  new KeywordPolicy(['https://t.me/']),
  new RegexPolicy(/(🟠|🔥|😳)ChtaGPT/i),
  new PubkeyBanPolicy(['e810fafa1e89cdf80cced8e013938e87e21b699b24c8570537be92aec4b12c18']),
  new HellthreadPolicy({ limit: 100 }),
  new AntiDuplicationPolicy({ kv: await Deno.openKv(), expireIn: 60000, minLength: 50 }),
]);

const [_, eventId, ok, reason] = await policy.call(event);

Pipelines can be used to chain policies together, to accept or reject events based on multiple criteria.

The NPolicy Interface

Policies use a simple interface, NPolicy, which accepts an event and returns a relay 'OK' message.

interface NPolicy {
  call(event: NostrEvent): Promise<NostrRelayOK>;
}

If the NostrRelayOK message returns false, the event should be rejected (or not shown to users).

Included Policies

Nostrify ships with a few policies to get you started.

Policy	Description	Example Options
AntiDuplicationPolicy	Prevent messages with the exact same content from being submitted repeatedly.	{ kv: await Deno.openKv(), expireIn: 60000, minLength: 50 }
AnyPolicy	Accepts an event if any policy accepts it.	[new PowPolicy(), new KeywordPolicy()]
DomainPolicy	Filters events by the author's NIP-05 domain.	{ blacklist: ['replyguy.dev'] }
FiltersPolicy	Reject events that don't match the filters.	[{ kinds: [0, 1, 3, 5, 6, 7] }]
HashtagPolicy	Reject events containing any of the banned hashtags.	['nsfw']
HellthreadPolicy	Reject messages that tag too many participants.	{ limit: 15 }
InvertPolicy	Inverts the result of another policy.	new PubkeyBanPolicy([...])
KeywordPolicy	Reject events containing any of the strings in its content.	['moo', 'oink', 'honk']
NoOpPolicy	Minimal sample policy for demonstration purposes. Allows all events through.
OpenAIPolicy	Passes event content to OpenAI and then rejects flagged events.	{ apiKey: '123...' }
PipePolicy	Compose multiple policies into a single policy.	[new PowPolicy(), new KeywordPolicy()]
PowPolicy	Reject events which don't meet Proof-of-Work (NIP-13) criteria.	{ difficulty: 20 }
PubkeyBanPolicy	Ban individual pubkeys from publishing events to the relay.	['e810...', 'fafa...', '1e89...']
ReadOnlyPolicy	This policy rejects all messages.
RegexPolicy	Reject events whose content matches the regex.	/(🟠|🔥|😳)ChtaGPT/i
SizePolicy	Reject events that are too large.	{ maxBytes: 8192 }
WhitelistPolicy	Allows only the listed pubkeys to post to the relay. All other events are rejected.	['e810...', 'fafa...', '1e89...']

See All Policies for more information.

Custom Policies

You can create your own policy by implementing NPolicy. This allows you to reject events based on any criteria you choose.

import { NostrEvent, NostrRelayOK, NPolicy } from '@nostrify/nostrify';

class MyPolicy implements NPolicy {
  constructor(/* your options */) {
    // Use the constructor to add any additional information you need.
  }

  async call(event: NostrEvent): Promise<NostrRelayOK> {
    if (/* check if should reject */) {
      return ['OK', event.id, false, 'blocked: event did not meet criteria'];
    }

    // Allow other events.
    return ['OK', event.id, true, ''];
  }
}

Other Uses

Policies are useful for preventing spam or enforcing rules on a relay. But they can also be used to collect statistics, trigger side-effects, and more.