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Moderator's guide to Mjolnir (bot edition)

Moderating a community shouldn't be difficult - Mjolnir gives you the tools to make moderation simple and impersonal.

Note: This guide does not apply to the Synapse module, which applies rules at the homeserver level. More information about the Synapse module can be found in the README.

Quick usage

If you're actively dealing with an incident, here's what you need to know:

  • Always talk to Mjolnir in your coordination room.
  • !mjolnir rooms add <room> will add a room to your "protected rooms", rooms where mjolnir will propagate bans.
  • !mjolnir ban <shortcode> user will ban someone.
  • !mjolnir ban <shortcode> server will ban a whole server.
  • !mjolnir rules will tell you what the shortcodes are for your ban lists (needed above).
  • !mjolnir redact will redact someone's posts in a specific room.
  • !mjolnir redact will redact someone's posts in all rooms Mjolnir protects.
  • !mjolnir protections will show you your available protections - green circles mean enabled.
  • !mjolnir enable <protection> to turn on a protection.
  • !mjolnir move <room alias> <room alias/ID> Moves a room alias to a new room ID
  • !mjolnir verify makes sure the bot has all required permissions to enact moderation (in all the protected rooms).

How Mjolnir works

Mjolnir uses rules to define its behaviours, with rules defined in ban lists. The rules Mjolnir gets from ban lists are additive, meaning they cannot be cancelled out. The first rule that matches will be the one that bans an entity.

Entities are rooms, users, and servers. The Mjolnir bot only handles users and servers, representing them as membership bans and server ACLs. ACLs are automatically applied because the rules transfer directly into the ACL format while membership bans are applied on sight. Within Matrix it is not currently possible to ban a set of users by glob/regex, so Mjolnir monitors the rooms it protects for membership changes and bans people who match rules when they join/are invited.

Mjolnir can run through Pantalaimon if your coordination room is encrypted (this is recommended). Your coordination/management room is where you and all of your moderators can speak to Mjolnir and update the rules it uses. Be sure to keep this room private to avoid unauthorized access to the bot.

Note that Mjolnir performs all its moderation actions as itself rather than encouraging you to use your own personal account. Banning someone with a personal account can feel like a targeted attack, leading to further abuse sent to you - using a bot can sometimes diminish the effect. You're welcome to ban someone without using Mjolnir - the bot won't interfere.

List management

Mjolnir can manage ban lists created through commands. These ban lists can be shared with the general public or kept private for internal reference. Lists that can be managed are referenced by shortcode - a string that identifies the room without spaces. For example, a terms of service list might have the shortcode tos.

To create a new list, run !mjolnir list create tos terms-of-service-bans. This creates a new list with the shortcode tos and the alias Bans can then be added with !mjolnir ban tos user (see !mjolnir help for full command reference).

Mjolnir can also watch other people's ban lists through !mjolnir watch To unsubscribe, use !mjolnir unwatch


Bans are appended to ban lists and enforced immediately. There are three kinds of bans that can be issued: user, server, and room. Currently the bot won't act upon room bans, but other parts of Mjolnir might. As mentioned earlier, user and server bans are enforced at the room level through existing support in Matrix.

Bans support wildcards (*) as well, allowing you to ban entire subdomains where required. If you wanted to ban all of for instance, you'd ban and *

To issue a ban, use !mjolnir ban <shortcode> <entity> <glob> [reason]. Reasons are optional. For example: !mjolnir ban tos server * Known for spam to ban the * server for spam.

If you've banned someone from mistake, you can remove the rule from the ban list using the unban command: !mjolnir unban <shortcode> <entity> <glob> [apply]. Note that this just removes the rule and might not cause an unban because another list may still ban the entity. The [apply] argument can be specified as true or false (default false) then the unban is applied immediately regardless of rules, though the unban might be reversed immediately afterwards due to another rule banning the entity.

Rules (bans) can be imported with !mjolnir import <room alias/ID> <shortcode> - this will inspect the room's state and generate rules for <shortcode> to populate.


Often it is desirable to remove some content without having to do it yourself. Mjolnir can look up past events sent by a user and redact them with !mjolnir redact If you want to redact events by that person from all protected rooms, don't specify a room at the end.


Sometimes you might want to see what Mjolnir is up to. There's some commands in !mjolnir help that could be of use to you, such as !mjolnir rules to see what rules it is actually enforcing and !mjolnir status to see if Mjolnir is even running where you expect it to.

Adding protected rooms on the fly is as easy as !mjolnir rooms add <room alias>. You can see all the rooms which are protected with !mjolnir rooms, and remove a room with !mjolnir rooms remove <room alias>. Note that rooms which are listed in the config may be protected again when the bot restarts - to remove these rooms permanently from protection, remove them from the config.

Trusted Reporters

Mjolnir has an (optional) system in which it will poll Synapse for new reports, and when it sees sufficient amounts of reports from trusted users on an given message, it will take an action, such as redacting the message.

The users to trust, the actions to take, and the thresholds needed for those actions are configurable.


  • pollReport: true in Mjolnir config file
  • restart Mjolnir
  • !mjolnir enable TrustedReporters
  • !mjolnir config add TrustedReporters.mxids
  • !mjolnir config set TrustedReporters.alertThreshold 3

TrustedReporters supports 3 different thresholds; alertThreshold, redactThreshold, and banThreshold. By default, only alertThreshold is enabled, and is set to 3. Mjolnir will only consider reports that take place in rooms Mjolnir is protecting. alertThreshold is separate from Mjolnir's ability to log each report, which is displayReports in Mjolnir's config file.

Make sure that anything you have sat in front of Synapse (e.g. nginx) is correctly configured to forward /_synapse/admin/v1/event_reports and /_synapse/admin/v1/rooms/${room_id}/context/${revent_id} to Synapse, or Mjolnir will not be able to poll for new reports. Mjolnir polls for new reports every 30 seconds.