diff --git a/README.md b/README.md
index fbf42d6..54d1c92 100644
--- a/README.md
+++ b/README.md
@@ -30,3 +30,24 @@ Inspired by Reddit's modmail system.
 `!unblock` Unblocks the user from using modmail
 
 To automatically reply without using !reply or !r, enable `alwaysReply` in the config. `alwaysReplyAnon` sets whether to reply anonymously. If you do not wish to reply, it will ignore any message starting in the prefix (which defaults to !), such as !note
+
+## Configuration options
+These go in `config.json`. See also `config.example.json`.
+
+|Option|Default|Description|
+|------|-------|-----------|
+|token|None|**Required!** The bot user's token|
+|mailGuildId|None|**Required!** The inbox server's ID|
+|mainGuildId|None|ID of the main server where people contact the bot from, used for e.g. displaying users' nicknames|
+|prefix|"!"|Prefix for bot commands|
+|status|"Message me for help"|The bot's "Playing" text|
+|responseMessage|"Thank you for your message! Our mod team will reply to you here as soon as possible."|The bot's response to DMs that start a new thread|
+|alwaysReply|false|If set to true, all messages in modmail threads will be relayed back to the user, even ones without `!r`|
+|alwaysReplyAnon|false|If `alwaysReply` is set to true, this option controls whether the auto-reply is anonymous|
+|useNicknames|false|If set to true, mod replies will use their nickname (on the inbox server) instead of their username|
+|ignoreAccidentalThreads|false|If set to true, the bot attempts to ignore common "accidental" messages that would start a new thread, such as "ok", "thanks", etc.|
+|enableGreeting|false|Set to true to send a welcome message to new main guild members. Requires `mainGuildId` to be set.|
+|greetingMessage|None|Text content of the welcome message|
+|greetingAttachment|None|Path to an image or other attachment to send along with the greeting|
+|port|8890|Port from which to serve attachments and logs|
+|url|None|URL to use for attachment and log links. Defaults to `IP:PORT`|