diff --git a/SETUP.md b/SETUP.md
index 4886840..12868e8 100644
--- a/SETUP.md
+++ b/SETUP.md
@@ -21,11 +21,7 @@
 1. If your system's CPU architecture is not x86\_64, the version of Chromium bundled with Puppeteer will not work, and the following steps are required:
     1. Install Chrome/Chromium from your distribution's package manager
     1. Set `executable_path` in `puppet/config.json` to the path to the installed Chrome/Chromium binary
-1. Run `node prep_helper.js` to open Chrome/Chromium with the downloaded LINE extension enabled, and click on the LINE icon next to the URL bar
-1. Once the LINE popup appears, press F12 to show DevTools, which will reveal the LINE extension's UUID
-1. Edit `puppet/config.json` with some important settings:
-    * set `"url"` to the UUID found in the previous step
-    * set the `"listen"` settings to the socket to use for communication with the bridge (see [puppet/README.md](puppet/README.md) for details)
+1. Edit `puppet/config.json` with desired settings (see [puppet/README.md](puppet/README.md) for details)
 
 ## Bridge
 1. `cd` to the project root directory and create a Python virtual environment with `python3 -m venv .venv`, and enter it with `source .venv/bin/activate`
diff --git a/puppet/README.md b/puppet/README.md
index e115547..4aae3b5 100644
--- a/puppet/README.md
+++ b/puppet/README.md
@@ -9,9 +9,6 @@ The `executable_path` specifies the path to the Chromium binary for Puppeteer to
 ### Profile directory
 The `profile_dir` specifies which directory to put Chromium user data directories.
 
-### URL
-`url` specifies the URL of the index page of the LINE extension for your Chromium installation.
-
 ### Extension directory
 The `extension_dir` specifies which directory contains the files for the LINE extension, which you must download yourself.
 
diff --git a/puppet/example-config.json b/puppet/example-config.json
index a814b2d..85f90c5 100644
--- a/puppet/example-config.json
+++ b/puppet/example-config.json
@@ -5,7 +5,6 @@
 	},
 	"executable_path": "",
 	"profile_dir": "./profiles",
-	"url": "chrome-extension://<extension-uuid>/index.html",
 	"extension_dir": "./extension_files",
 	"cycle_delay": 5000,
 	"use_xdotool": false,
diff --git a/puppet/prep_helper.js b/puppet/prep_helper.js
deleted file mode 100644
index 92ae681..0000000
--- a/puppet/prep_helper.js
+++ /dev/null
@@ -1,46 +0,0 @@
-// matrix-puppeteer-line - A very hacky Matrix-LINE bridge based on running LINE's Chrome extension in Puppeteer
-// Copyright (C) 2020-2021 Tulir Asokan, Andrew Ferrazzutti
-//
-// This program is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Affero General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// This program is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-// GNU Affero General Public License for more details.
-//
-// You should have received a copy of the GNU Affero General Public License
-// along with this program.  If not, see <https://www.gnu.org/licenses/>.
-import puppeteer from "puppeteer"
-import fs from "fs"
-
-import arg from "arg"
-
-const args = arg({
-	"--config": String,
-	"--browser": String,
-	"-c": "--config",
-	"-b": "--browser",
-})
-
-const configPath = args["--config"] || "config.json"
-
-console.log("[Main] Reading config from", configPath)
-const config = JSON.parse(fs.readFileSync(configPath).toString())
-const extensionDir = config.extension_dir || "extension_files"
-const executablePath = args["--browser"] || config.executable_path;
-
-(async () =>
-{
-	await puppeteer.launch({
-		executablePath: executablePath,
-		headless: false,
-		args: [
-				`--disable-extensions-except=${extensionDir}`,
-			`--load-extension=${extensionDir}`
-		],
-		timeout: 0,
-    })
-})()
diff --git a/puppet/src/main.js b/puppet/src/main.js
index 7124ab6..c9542b9 100644
--- a/puppet/src/main.js
+++ b/puppet/src/main.js
@@ -37,7 +37,6 @@ MessagesPuppeteer.executablePath = args["--browser"] || config.executable_path |
 MessagesPuppeteer.noSandbox = args["--no-sandbox"] || MessagesPuppeteer.noSandbox
 MessagesPuppeteer.profileDir = config.profile_dir || MessagesPuppeteer.profileDir
 MessagesPuppeteer.devtools = config.devtools || false
-MessagesPuppeteer.url = config.url
 MessagesPuppeteer.extensionDir = config.extension_dir || MessagesPuppeteer.extensionDir
 MessagesPuppeteer.cycleDelay = config.cycle_delay || MessagesPuppeteer.cycleDelay
 MessagesPuppeteer.useXdotool = config.use_xdotool || MessagesPuppeteer.useXdotool
diff --git a/puppet/src/puppet.js b/puppet/src/puppet.js
index ea218db..213273e 100644
--- a/puppet/src/puppet.js
+++ b/puppet/src/puppet.js
@@ -102,9 +102,18 @@ export default class MessagesPuppeteer {
 			this.page = await this.browser.newPage()
 		}
 
-		this.blankPage = await this.browser.newPage()
-		await this.page.bringToFront()
+		{
+			this.log("Finding extension UUID")
+			await this.page.goto("chrome://system")
+			const selector = "#extensions-value"
+			await this.page.waitForSelector(selector, 0)
+			const lineDetails = await this.page.$eval(selector, e => e.innerText)
+			const uuid = lineDetails.match(/(.*) : LINE : version/)[1]
+			this.log("Found extension UUID ${uuid}")
+			MessagesPuppeteer.url = `chrome-extension://${uuid}/index.html`
+		}
 
+		this.blankPage = await this.browser.newPage()
 		if (MessagesPuppeteer.useXdotool) {
 			this.log("Finding window ID")
 			const buffer = execSync("xdotool search 'about:blank'")