diff --git a/d2m/discord-command-handler.js b/d2m/discord-command-handler.js
index 1bd52c8a..fa59822d 100644
--- a/d2m/discord-command-handler.js
+++ b/d2m/discord-command-handler.js
@@ -3,6 +3,8 @@
 const assert = require("assert").strict
 const util = require("util")
 const DiscordTypes = require("discord-api-types/v10")
+const reg = require("../matrix/read-registration")
+
 const {discord, sync, db} = require("../passthrough")
 /** @type {import("../matrix/api")}) */
 const api = sync.require("../matrix/api")
@@ -86,7 +88,7 @@ const commands = [{
 			const avatarEvent = await api.getStateEvent(roomID, "m.room.avatar", "")
 			const avatarURLParts = avatarEvent?.url.match(/^mxc:\/\/([^/]+)\/(\w+)$/)
 			let currentAvatarMessage =
-				( avatarURLParts ? `Current room-specific avatar: https://matrix.cadence.moe/_matrix/media/r0/download/${avatarURLParts[1]}/${avatarURLParts[2]}`
+				( avatarURLParts ? `Current room-specific avatar: ${reg.ooye.server_origin}/_matrix/media/r0/download/${avatarURLParts[1]}/${avatarURLParts[2]}`
 				: "No avatar. Now's your time to strike. Use `//icon` again with a link or upload to set the room-specific avatar.")
 
 			// Next potential avatar
diff --git a/m2d/converters/utils.js b/m2d/converters/utils.js
index 02ec1478..96892521 100644
--- a/m2d/converters/utils.js
+++ b/m2d/converters/utils.js
@@ -25,7 +25,7 @@ function eventSenderIsFromDiscord(sender) {
  */
 function getPublicUrlForMxc(mxc) {
 	const avatarURLParts = mxc?.match(/^mxc:\/\/([^/]+)\/(\w+)$/)
-	if (avatarURLParts) return `https://matrix.cadence.moe/_matrix/media/r0/download/${avatarURLParts[1]}/${avatarURLParts[2]}`
+	if (avatarURLParts) return `${reg.ooye.server_origin}/_matrix/media/r0/download/${avatarURLParts[1]}/${avatarURLParts[2]}`
 	else return null
 }
 
diff --git a/matrix/mreq.js b/matrix/mreq.js
index d5ffebad..4291ede8 100644
--- a/matrix/mreq.js
+++ b/matrix/mreq.js
@@ -8,7 +8,7 @@ const { sync } = passthrough
 /** @type {import("./read-registration")} */
 const reg = sync.require("./read-registration.js")
 
-const baseUrl = "https://matrix.cadence.moe/_matrix"
+const baseUrl = `${reg.ooye.server_origin}/_matrix`
 
 class MatrixServerError extends Error {
 	constructor(data, opts) {
diff --git a/readme.md b/readme.md
index 58528f43..0ad010e0 100644
--- a/readme.md
+++ b/readme.md
@@ -51,15 +51,15 @@ Most features you'd expect in both directions, plus a little extra spice:
 
 Node.js version 18 or later is required: https://nodejs.org/en/download/releases (the matrix-appservice dependency demands 18)
 
-Install dependencies: `npm install --save-dev`
+Install dependencies: `npm install --save-dev` (only need --save-dev if you will run the automated tests)
 
 Copy `config.example.js` to `config.js` and fill in Discord token.
 
-Copy `registration.example.yaml` to `registration.yaml` and fill in bracketed values. Register it in Synapse's `homeserver.yaml` through the usual appservice installation process, then restart Synapse.
+Copy `registration.example.yaml` to `registration.yaml` and fill in bracketed values. You could generate each hex string with `dd if=/dev/urandom bs=32 count=1 2> /dev/null | basenc --base16 | dd conv=lcase 2> /dev/null`. Register the registration in Synapse's `homeserver.yaml` through the usual appservice installation process, then restart Synapse.
 
-If developing on a different computer to the one running the homeserver, use SSH port forwarding so that Synapse can connect on its `localhost:6693` to reach the running bridge on your computer. Example: `ssh -T -v -R 6693:localhost:6693 username@matrix.cadence.moe`
+If developing on a different computer to the one running the homeserver, use SSH port forwarding so that Synapse can connect on its `localhost:6693` to reach the running bridge on your computer. Example: `ssh -T -v -R 6693:localhost:6693 me@matrix.cadence.moe`
 
-Run `node scripts/seed.js` to check your setup, then create the database and server state (only need to run this once ever)
+Run `node scripts/seed.js` to check your setup, create the database and server state (only need to run this once ever)
 
 Make sure the tests work: `npm t`
 
diff --git a/registration.example.yaml b/registration.example.yaml
index 89ce4e05..802d7430 100644
--- a/registration.example.yaml
+++ b/registration.example.yaml
@@ -17,3 +17,4 @@ ooye:
   namespace_prefix: _ooye_
   max_file_size: 5000000
   server_name: [the part after the colon in your matrix id, like cadence.moe]
+  server_origin: [the full protocol and domain of your actual matrix server's location, with no trailing slash, like https://matrix.cadence.moe]
diff --git a/scripts/seed.js b/scripts/seed.js
index be2d5f37..e0bee4d3 100644
--- a/scripts/seed.js
+++ b/scripts/seed.js
@@ -22,8 +22,10 @@ const utils = require("../m2d/converters/utils")
 	const mxid = `@${reg.sender_localpart}:${reg.ooye.server_name}`
 
 	// ensure registration is correctly set...
-	assert(reg.sender_localpart.startsWith(reg.ooye.namespace_prefix))
-	assert(utils.eventSenderIsFromDiscord(mxid))
+	assert(reg.sender_localpart.startsWith(reg.ooye.namespace_prefix)) // appservice's localpart must be in the namespace it controls
+	assert(utils.eventSenderIsFromDiscord(mxid)) // appservice's mxid must be in the namespace it controls
+	assert(reg.ooye.server_origin.match(/^https?:\/\//)) // must start with http or https
+	assert.notEqual(reg.ooye.server_origin.slice(-1), "/") // must not end in slash
 
 	// database ddl...
 	db.exec(fs.readFileSync("db/ooye-schema.sql", "utf8"))
diff --git a/types.d.ts b/types.d.ts
index 8d40372d..e3a99091 100644
--- a/types.d.ts
+++ b/types.d.ts
@@ -20,6 +20,7 @@ export type AppServiceRegistrationConfig = {
 		namespace_prefix: string
 		max_file_size: number
 		server_name: string
+		server_origin: string
 	}
 	old_bridge?: {
 		as_token: string