diff --git a/README.md b/README.md
index 6954e5b4..6134b419 100644
--- a/README.md
+++ b/README.md
@@ -64,12 +64,23 @@ First you need to create a Discord bot user, which you can do by following the i
       ["AUTH", "test", "password"]
     ],
     "channelMapping": { // Maps each Discord-channel to an IRC-channel, used to direct messages to the correct place
-      "#discord": "#irc channel-password" // Add channel keys after the channel name
+      "#discord": "#irc channel-password", // Add channel keys after the channel name
+      "1234567890": "#channel" // Use a discord channel ID instead of its name (so you can rename it or to disambiguate)
     },
     "ircOptions": { // Optional node-irc options
       "floodProtection": false, // On by default
       "floodProtectionDelay": 1000 // 500 by default
     },
+    "format": { // Optional custom formatting options
+      // Patterns, represented by {$patternName}, are replaced when sending messages
+      "commandPrelude": "Command sent by {$nickname}", // Message sent before a command
+      "ircText": "<{$displayUsername}> {$text}", // When sending a message to IRC
+      "urlAttachment": "<{$displayUsername}> {$attachmentURL}", // When sending a Discord attachment to IRC
+      "discord": "**<{$author}>** {$withMentions}" // When sending a message to Discord
+      // Other patterns that can be used:
+      // {$discordChannel} (e.g. #general)
+      // {$ircChannel} (e.g. #irc)
+    },
     "ircNickColor": false, // Gives usernames a color in IRC for better readability (on by default)
     // Makes the bot hide the username prefix for messages that start
     // with one of these characters (commands):
@@ -81,6 +92,8 @@ First you need to create a Discord bot user, which you can do by following the i
 
 The `ircOptions` object is passed directly to node-irc ([available options](http://node-irc.readthedocs.org/en/latest/API.html#irc.Client)).
 
+To retrieve a discord channel ID, write `\#channel` on the relevant server – it should produce something of the form `<#1234567890>`, which you can then use in the `channelMapping` config.
+
 ## Tests
 Run the tests with:
 ```bash