Twitch offers a number of moderation tools and anti-spam/anti-troll guards. I go into some detail during the second part of Streamer Tips 2 which should be viewed as a companion to this - moderation starts at the 08:36 mark.
AutoMod is an AI that guards your chat. It is unique among moderation tools in that it is a shield that prevents bad messages from being posted (as opposed to a sword that removes them afterwards), but one whose blocks can be overridden by a human mod.
To configure AutoMod, go to [https://www.twitch.tv/dashboard/settings/moderation/automod](your Twitch Dashboard). Choose a protection level based on how you want to run your channel - are you PG-13? G-rated? Swearing's okay but no targeted harassment? Then make sure your (human) mods have the chat option "Show messages caught by AutoMod" active (have them click the gear on their chat), and proceed to train the AI.
When properly trained, AutoMod serves alongside your other moderation tools in ways that nothing else can.
The absolute most important moderation tool is an actual person wielding a sword. If your stream is small and quiet, you can do your own moderation, but as the channel grows, you will want to appoint additional sword-bearers. New to Twitch and don't know how things go? An experienced mod can help you out and make sure you don't have to worry about anything.
Communicate well with your mods. Are they too aggressive? Too lenient? Don't expect them to read your mind (though some are quite good at it), just let them know what you want. A good mod will reflect your intentions as long as you're clear.
Not to be confused with AutoMod which is a first-party Twitch tool, moderation bots are simply chat bots that have been granted mod powers. You, the streamer, choose which bots to empower, and you also choose how to configure them; all the well-known moderation bots (Nightbot, DeepBot, StreamElements(?), StreamLabs(?)) have flexible configuration options to allow you to customize the moderation they do. If you give a bot a sword, take responsibility for the way it behaves, and teach it what you want it to do; communicate with your bots just as you do with your humans.
Twitch offers you a number of ways to restrict who's allowed to speak in chat. These tools can be used to combat spam or trolls, but they can also block legit people from chatting, so use them wisely (and sparingly).
Most of these can be activated and deactivated on the fly by any moderator.
Anyone who's not following your channel, or who hasn't been following for long enough, can't chat. This is an effective temporary measure for keeping out newly-created accounts, but it's also a strong turn-off for new viewers. Your channel will become more insular, less welcoming. I recommend not using this permanently, except in special circumstances.
This is best used when a massive influx of trolls starts making noises and you need to deal with them all.
- Activate:
/followers 600(ten minutes is usually a good choice) - Deactivate:
/followersoff
Even stronger than follower-only mode, this is the veritable nuclear option for keeping the unwashed millions out of your chat. This should basically be used ONLY to tame a nightmare situation, and then disabled again afterwards. If you are tempted to use sub-only mode permanently, consider instead creating a sub-only chat room, as this offers similar benefits without the turn-off.
This is best used when things are SERIOUSLY messed up and you just need to turn everything off and let the mods catch up.
- Activate:
/subscribers - Deactivate:
/subscribersoff
Unlike the previous options, this does not block any users completely, but all non-mods are restricted to one message every N seconds. For small values of N, eg 1-second slow mode or 3-second slow mode, this can be a reasonable way to keep your channel from getting too noisy (but usually that's not necessary); for large values of N (eg 30-second or more), it can help to tame a bad situation and let your mods catch up with what's going on.
This is best used when a small number of users are repeatedly spamming and you can't catch them all to time them out.
- Activate:
/slow 3or/slow 10or (for really bad situations)/slow 30 - Deactivate:
/slowoff
Generally, don't use this. AutoMod does a better job. If you really want it, be aware that it has its own limitations (bots, even non-mod bots, can still see chat without delays), and it can create weird situations.
Twitch has a first-party option to block all links from non-mods, but if you need more flexibility, it's best to leave that option off, and have a bot that can choose who to permit and who to purge.
Ahh... this one. It's not really a moderation tool, except that it is. It's theoretically able to prevent certain forms of abusive messages... but more commonly, it's treated as a toy. "Turn on emote-only chat for two minutes!" is a fun reward for your community (maybe something people can spend their channel currency on).
As a mod tool, this is probably best used when the spam involves unsavoury text or ASCII art? Maybe? But it's a great fun toy.
- Activate:
/emoteonly - Deactivate:
/emoteonlyoff
This can be seen as a special form of slow mode. Unique messages are permitted; duplicates are blocked. Be aware that this can make your channel unfriendly towards incoming raids, as raids often involve all members posting the same message.
This is best used when large numbers of accounts post exactly the same text over and over.
- Activate:
/uniquechat - Deactivate:
/uniquechatoff
These are available in your own chat and in the chats of any channels you mod for. You can, with a single click, ban someone or time them out; this is very dangerous, and will often lead to banning the wrong person. Instead, use the user's popup information (click on the name, or use the "/user" command) for this purpose, unless you're dealing with a large number of trolls all at once. The mod icons do have one unique feature, however: you can delete a single message, something you can't easily do any other way. This message removal does not remove a mod sword, does not excessively purge all text, and is a great way to deal with an accidental slip-up by an otherwise-legit person.
- This only affects the person who does it, and can be activated/deactivated via the gear icon in your chat window.