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Message Rewrite Facility

The Message Rewrite Facility (MRF) is a subsystem that is implemented as a series of hooks that allows the administrator to rewrite or discard messages.

Possible uses include:

  • marking incoming messages with media from a given account or instance as sensitive
  • rejecting messages from a specific instance
  • rejecting reports (flags) from a specific instance
  • removing/unlisting messages from the public timelines
  • removing media from messages
  • sending only public messages to a specific instance

The MRF provides user-configurable policies. The default policy is NoOpPolicy, which disables the MRF functionality. Akkoma also includes an easy to use policy called SimplePolicy which maps messages matching certain pre-defined criterion to actions built into the policy module.

It is possible to use multiple, active MRF policies at the same time.

Using SimplePolicy

SimplePolicy is capable of handling most common admin tasks.

To use SimplePolicy, you must enable it. Do so by adding the following to your :instance config object, so that it looks like this:

config :pleroma, :mrf,
  policies: Pleroma.Web.ActivityPub.MRF.SimplePolicy

Once SimplePolicy is enabled, you can configure various groups in the :mrf_simple config object. These groups are:

  • reject: Servers in this group will have their messages rejected. Also outbound messages will not be sent to these servers.
  • accept: If not empty, only messages from these instances will be accepted (whitelist federation).
  • media_nsfw: Servers in this group will have the #nsfw tag and sensitive setting injected into incoming messages which contain media.
  • media_removal: Servers in this group will have media stripped from incoming messages.
  • avatar_removal: Avatars from these servers will be stripped from incoming messages.
  • banner_removal: Banner images from these servers will be stripped from incoming messages.
  • background_removal: User background images from these servers will be stripped from incoming messages.
  • report_removal: Servers in this group will have their reports (flags) rejected.
  • federated_timeline_removal: Servers in this group will have their messages unlisted from the public timelines by flipping the to and cc fields.
  • reject_deletes: Deletion requests will be rejected from these servers.

Servers should be configured as lists.


This example will enable SimplePolicy, block media from, mark media as NSFW from and, reject messages from, remove messages from from the federated timeline and block reports (flags) from whiny.whiner. We also give a reason why the moderation was done:

config :pleroma, :mrf,
  policies: [Pleroma.Web.ActivityPub.MRF.SimplePolicy]

config :pleroma, :mrf_simple,
  media_removal: [{"", "Media can contain illegal contant"}],
  media_nsfw: [{"", "unmarked nsfw media"}, {"", "A lot of unmarked nsfw media"}],
  reject: [{"", "They keep spamming our users"}],
  federated_timeline_removal: [{"", "Annoying low-quality posts who otherwise fill up TWKN"}],
  report_removal: [{"whiny.whiner", "Keep spamming us with irrelevant reports"}]

Use with Care

The effects of MRF policies can be very drastic. It is important to use this functionality carefully. Always try to talk to an admin before writing an MRF policy concerning their instance.

Hiding or Obfuscating Policies

You can opt out of publicly displaying all MRF policies or only hide or obfuscate selected domains.

To just hide everything set:

config :pleroma, :mrf,
  transparency: false,

To hide or obfuscate only select entries, use:

config :pleroma, :mrf,
  transparency_obfuscate_domains: ["", ""],
  transparency_exclusions: [{"", "even a fragment is too spoopy for humans"}]

More MRF Policies

See the documentation cheatsheet for all available MRF policies and their options.

Writing your own MRF Policy

As discussed above, the MRF system is a modular system that supports pluggable policies. This means that an admin may write a custom MRF policy in Elixir or any other language that runs on the Erlang VM, by specifying the module name in the policies config setting.

For example, here is a sample policy module which rewrites all messages to "new message content":

defmodule Pleroma.Web.ActivityPub.MRF.RewritePolicy do
  @moduledoc "MRF policy which rewrites all Notes to have 'new message content'."
  @behaviour Pleroma.Web.ActivityPub.MRF.Policy

  # Catch messages which contain Note objects with actual data to filter.
  # Capture the object as `object`, the message content as `content` and the
  # message itself as `message`.
  @impl true
  def filter(
        %{"type" => "Create", "object" => %{"type" => "Note", "content" => content} = object} =
      when is_binary(content) do
    # Subject / CW is stored as summary instead of `name` like other AS2 objects
    # because of Mastodon doing it that way.
    summary = object["summary"]

    # Message edits go here.
    content = "new message content"

    # Assemble the mutated object.
    object =
      |> Map.put("content", content)
      |> Map.put("summary", summary)

    # Assemble the mutated message.
    message = Map.put(message, "object", object)
    {:ok, message}

  # Let all other messages through without modifying them.
  @impl true
  def filter(message), do: {:ok, message}

  @impl true
  def describe do
    {:ok, %{mrf_sample: %{content: "new message content"}}}

If you save this file as lib/pleroma/web/activity_pub/mrf/rewrite_policy.ex, it will be included when you next rebuild Akkoma. You can enable it in the configuration like so:

config :pleroma, :mrf,
  policies: [

Please note that the Akkoma developers consider custom MRF policy modules to fall under the purview of the AGPL. As such, you are obligated to release the sources to your custom MRF policy modules upon request.

MRF policies descriptions

If MRF policy depends on config, it can be added into MRF tab to adminFE by adding config_description/0 method, which returns a map with a specific structure. See existing MRF's like lib/pleroma/web/activity_pub/mrf/activity_expiration_policy.ex for examples. Note that more complex inputs, like tuples or maps, may need extra changes in the adminFE and just adding it to config_description/0 may not be enough to get these inputs working from the adminFE.


      key: :mrf_activity_expiration,
      related_policy: "Pleroma.Web.ActivityPub.MRF.ActivityExpirationPolicy",
      label: "MRF Activity Expiration Policy",
      description: "Adds automatic expiration to all local activities",
      children: [
          key: :days,
          type: :integer,
          description: "Default global expiration time for all local activities (in days)",
          suggestions: [90, 365]