diff --git a/.changeset/shy-forks-grin.md b/.changeset/shy-forks-grin.md
new file mode 100644
index 000000000000..769992c95435
--- /dev/null
+++ b/.changeset/shy-forks-grin.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+Honor HTTPS options in Preview and Dev
diff --git a/packages/kit/src/core/dev/index.js b/packages/kit/src/core/dev/index.js
index ba8cf1c53768..e6c8b29f31b1 100644
--- a/packages/kit/src/core/dev/index.js
+++ b/packages/kit/src/core/dev/index.js
@@ -91,8 +91,8 @@ class Watcher extends EventEmitter {
 	async init_server() {
 		if (!this.manifest) throw new Error('Must call init() before init_server()');
 
-		/** @type {any} */
-		const user_config = (this.config.kit.vite && this.config.kit.vite()) || {};
+		/** @type {import('types/config').ViteConfig} ViteConfig */
+		const vite_config = (this.config.kit.vite && this.config.kit.vite()) || {};
 
 		const default_config = {
 			server: {
@@ -105,12 +105,12 @@ class Watcher extends EventEmitter {
 		/** @type {(req: import("http").IncomingMessage, res: import("http").ServerResponse) => void} */
 		let handler = (req, res) => {};
 
-		this.server = await get_server(this.https, user_config, (req, res) => handler(req, res));
+		this.server = await get_server(this.https, vite_config, (req, res) => handler(req, res));
 
-		const alias = user_config.resolve && user_config.resolve.alias;
+		const alias = vite_config.resolve && vite_config.resolve.alias;
 
 		// don't warn on overriding defaults
-		const [modified_user_config] = deep_merge(default_config, user_config);
+		const [modified_user_config] = deep_merge(default_config, vite_config);
 
 		/** @type {[any, string[]]} */
 		const [merged_config, conflicts] = deep_merge(modified_user_config, {
@@ -153,7 +153,8 @@ class Watcher extends EventEmitter {
 				entries: []
 			},
 			ssr: {
-				noExternal: get_no_external(this.cwd, user_config.ssr && user_config.ssr.noExternal)
+				// @ts-ignore // ssr not defined in vite config.ts
+				noExternal: get_no_external(this.cwd, vite_config.ssr && vite_config.ssr.noExternal)
 			}
 		});
 
diff --git a/packages/kit/src/core/preview/index.js b/packages/kit/src/core/preview/index.js
index 2c9a43471464..88bc709d01c9 100644
--- a/packages/kit/src/core/preview/index.js
+++ b/packages/kit/src/core/preview/index.js
@@ -59,7 +59,11 @@ export async function preview({
 		read: (file) => fs.readFileSync(join(config.kit.files.assets, file))
 	});
 
-	const server = await get_server(use_https, config.kit, (req, res) => {
+	const vite_config =
+		/** @type {import('types/config').ViteConfig} ViteConfig */
+		(config.kit.vite && config.kit.vite()) || {};
+
+	const server = await get_server(use_https, vite_config, (req, res) => {
 		const parsed = parse(req.url || '');
 
 		assets_handler(req, res, () => {
diff --git a/packages/kit/src/core/server/index.js b/packages/kit/src/core/server/index.js
index 4463f840d673..876be11fc9e5 100644
--- a/packages/kit/src/core/server/index.js
+++ b/packages/kit/src/core/server/index.js
@@ -1,27 +1,39 @@
 import http from 'http';
 import https from 'https';
+import fs from 'fs';
+import path from 'path';
 /**
  *
  * @param {boolean} use_https
- * @param {any} user_config
+ * @param {import('types/config').ViteConfig} vite_config
  * @param {(req: http.IncomingMessage, res: http.ServerResponse) => void} handler
  * @returns {Promise<import('net').Server>}
  */
-export async function get_server(use_https, user_config, handler) {
-	/** @type {https.ServerOptions} */
-	const https_options = {};
+export async function get_server(use_https, vite_config, handler) {
+	/** @type {https.ServerOptions | undefined} */
+	let https_options;
 
 	if (use_https) {
-		if (
-			user_config.server &&
-			user_config.server.https &&
-			user_config.server.https.key &&
-			user_config.server.https.cert
-		) {
-			https_options.key = user_config.server.https.key.toString();
-			https_options.cert = user_config.server.https.cert.toString();
-		} else {
-			https_options.key = https_options.cert = (await import('./cert')).createCertificate();
+		https_options =
+			vite_config && vite_config.server && typeof vite_config.server.https === 'object'
+				? vite_config.server.https
+				: {};
+
+		if (https_options.ca) https_options.ca = readFileIfExists(https_options.ca);
+		if (https_options.cert) https_options.cert = readFileIfExists(https_options.cert);
+		if (https_options.key) https_options.key = readFileIfExists(https_options.key);
+		if (https_options.pfx) {
+			https_options.pfx = readFileIfExists(https_options.pfx);
+			delete https_options.cert;
+			delete https_options.key;
+		}
+
+		if (!https_options.pfx && (!https_options.key || !https_options.cert)) {
+			https_options.cert = https_options.key = (await import('./cert')).createCertificate();
+		}
+	} else {
+		if (vite_config && vite_config.server) {
+			delete vite_config.server.https;
 		}
 	}
 
@@ -31,3 +43,19 @@ export async function get_server(use_https, user_config, handler) {
 			: http.createServer(handler)
 	);
 }
+
+/**
+ *
+ * @param {string | Buffer | any[]} value
+ * @returns {string | Buffer | Buffer[]} value
+ */
+function readFileIfExists(value) {
+	if (typeof value === 'string') {
+		try {
+			return fs.readFileSync(path.resolve(value));
+		} catch (e) {
+			return value;
+		}
+	}
+	return value;
+}
diff --git a/packages/kit/types/config.d.ts b/packages/kit/types/config.d.ts
index b4107317d2f9..e7245f12127f 100644
--- a/packages/kit/types/config.d.ts
+++ b/packages/kit/types/config.d.ts
@@ -156,3 +156,5 @@ export interface ValidatedConfig {
 	};
 	preprocess: any;
 }
+
+export type { ViteConfig };