diff --git a/QLPreview/PreviewViewController.swift b/QLPreview/PreviewViewController.swift
index 253ebd3..2ae1705 100644
--- a/QLPreview/PreviewViewController.swift
+++ b/QLPreview/PreviewViewController.swift
@@ -11,9 +11,26 @@ class PreviewViewController: NSViewController, QLPreviewingController {
 		return NSNib.Name("PreviewViewController")
 	}
 	
+	/// Load resource file either from user documents dir (if exists) or app bundle (default).
+	func bundleFile(filename: String, ext: String) throws -> String {
+		if let appSupport = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first {
+			let override = appSupport.appendingPathComponent(filename + "." + ext)
+			if FileManager.default.fileExists(atPath: override.path) {
+				return try String(contentsOfFile: override.path, encoding: .utf8)
+			}
+			// else: do NOT copy! Breaks on future updates
+		}
+		// else, load bundle file
+		let path = Bundle.main.url(forResource: filename, withExtension: ext)
+		return try String(contentsOf: path!, encoding: .utf8)
+	}
+	
 	func preparePreviewOfFile(at url: URL) async throws {
 		let meta = MetaInfo(url)
-		let html = HtmlGenerator(meta).applyHtmlTemplate()
+		let html = HtmlGenerator(meta).generate(
+			template: try bundleFile(filename: "template", ext: "html"),
+			css: try bundleFile(filename: "style", ext: "css"),
+		)
 		// sure, we could use `WKWebView`, but that requires the `com.apple.security.network.client` entitlement
 		//let web = WKWebView(frame: self.view.bounds)
 		let web = WebView(frame: self.view.bounds)
diff --git a/README.md b/README.md
index 9760be0..c0351ae 100644
--- a/README.md
+++ b/README.md
@@ -24,42 +24,31 @@ I merely want things to be done.
 Also, I've removed support for provisioning profiles (`.mobileprovision`, `.provisionprofile`) to focus on app bundles.
 
 
-## ToDO
+
+## ToDo
 
 - [ ] support for `.apk` files
 
 
-## Development notes
 
+## Features
+
+### Customize HTML / CSS
+
+1. Right click on the app and select "Show Package Contents"
+2. Copy `Contents/Resources/template.html` (or `style.css`)
+3. Open `~/Library/Containers/de.relikd.QLAppBundle.Preview/Data/Documents/`
+4. Paste the previous file and modify it to your liking
+5. `QLAppBundle` will use the new file from now on
+
+
+
+## Development notes
 
 ### Debug
 
 You can show Console logs with `subsystem:de.relikd.QLAppBundle`
 
 
-### Compile errors
-
-If you encounter compile errors like:
-
-```
-Command SwiftEmitModule failed with a nonzero exit code
-```
-
-or
-
-```
-Could not build Objective-C module 'ExtensionFoundation'
-```
-
-or `ThumbnailProvider` is throwing lots of errors for undefined classes:
-
-remove the `SYSTEM_FRAMEWORK_SEARCH_PATHS` attribute from Project > Build Settings then try to compile again (it will fail).
-Afterwards, restore the value in the attribute.
-Now, the build index should be up-to-date and the app should compile fine.
-
-I havent figured out the exact issue, consider it a workaround.
-It should only be necessary once (or if you delete your `DerivedData` folder).
-
-
 [1]: https://github.com/ealeksandrov/ProvisionQL
 [2]: https://github.com/ealeksandrov/ProvisionQL/pull/54
diff --git a/src/HtmlGenerator.swift b/src/HtmlGenerator.swift
index 6889016..0e3e222 100644
--- a/src/HtmlGenerator.swift
+++ b/src/HtmlGenerator.swift
@@ -20,9 +20,6 @@ struct HtmlGenerator {
 		procFooterInfo()
 		// App Icon (last, because the image uses a lot of memory)
 		data["AppIcon"] = AppIcon(meta).extractImage(from: plistApp).withRoundCorners().asBase64()
-		// insert CSS styles
-		let cssURL = Bundle.main.url(forResource: "style", withExtension: "css")!
-		data["CSS"] = try! String(contentsOf: cssURL, encoding: .utf8)
 	}
 	
 	mutating func apply(_ values: [String: String]) {
@@ -39,9 +36,8 @@ struct HtmlGenerator {
 	}
 	
 	/// prepare html, replace values
-	func applyHtmlTemplate() -> String {
-		let templateURL = Bundle.main.url(forResource: "template", withExtension: "html")!
-		let html = try! String(contentsOf: templateURL, encoding: .utf8)
+	func generate(template html: String, css: String) -> String {
+		let templateValues = data.merging(["CSS": css]) { (_, new) in new }
 		
 		// this is less efficient
 		//	for (key, value) in templateValues {
@@ -58,7 +54,7 @@ struct HtmlGenerator {
 			rv.append(contentsOf: html[prevLoc ..< start])
 			prevLoc = html.index(start, offsetBy: match!.range.length)
 			// append key if exists (else remove template-key)
-			if let value = data[key] {
+			if let value = templateValues[key] {
 				rv.append(value)
 			} else {
 				// os_log(.debug, log: log, "unknown template key: %{public}@", key)