diff --git a/.changeset/loud-dancers-cough.md b/.changeset/loud-dancers-cough.md
new file mode 100644
index 000000000000..62dd3173cef9
--- /dev/null
+++ b/.changeset/loud-dancers-cough.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+[chore] enable TypeScript strict mode
diff --git a/packages/kit/src/core/adapt/prerender.js b/packages/kit/src/core/adapt/prerender.js
index 57b80c8c08b9..9721c91db0fa 100644
--- a/packages/kit/src/core/adapt/prerender.js
+++ b/packages/kit/src/core/adapt/prerender.js
@@ -124,7 +124,7 @@ export async function prerender({ cwd, out, log, config, build_data, fallback, a
 				method: 'GET',
 				headers: {},
 				path,
-				rawBody: null,
+				rawBody: '',
 				query: new URLSearchParams()
 			},
 			{
@@ -247,7 +247,7 @@ export async function prerender({ cwd, out, log, config, build_data, fallback, a
 				method: 'GET',
 				headers: {},
 				path: '[fallback]', // this doesn't matter, but it's easiest if it's a string
-				rawBody: null,
+				rawBody: '',
 				query: new URLSearchParams()
 			},
 			{
diff --git a/packages/kit/src/core/config/index.spec.js b/packages/kit/src/core/config/index.spec.js
index 2906bd4eafba..a2f863ba2115 100644
--- a/packages/kit/src/core/config/index.spec.js
+++ b/packages/kit/src/core/config/index.spec.js
@@ -5,6 +5,7 @@ import { deep_merge, validate_config } from './index.js';
 test('fills in defaults', () => {
 	const validated = validate_config({});
 
+	// @ts-ignore
 	delete validated.kit.vite;
 
 	assert.equal(validated, {
@@ -104,6 +105,7 @@ test('fills in partial blanks', () => {
 
 	assert.equal(validated.kit.vite(), {});
 
+	// @ts-ignore
 	delete validated.kit.vite;
 
 	assert.equal(validated, {
diff --git a/packages/kit/src/core/config/test/index.js b/packages/kit/src/core/config/test/index.js
index 87d4f0af57d9..614cefbb6e45 100644
--- a/packages/kit/src/core/config/test/index.js
+++ b/packages/kit/src/core/config/test/index.js
@@ -15,6 +15,7 @@ async function testLoadDefaultConfig(path) {
 
 	const config = await load_config({ cwd });
 
+	// @ts-ignore
 	delete config.kit.vite; // can't test equality of a function
 
 	assert.equal(config, {
diff --git a/packages/kit/src/core/create_manifest_data/index.js b/packages/kit/src/core/create_manifest_data/index.js
index 7c1fb93d4608..1a8a2f7b04da 100644
--- a/packages/kit/src/core/create_manifest_data/index.js
+++ b/packages/kit/src/core/create_manifest_data/index.js
@@ -247,8 +247,11 @@ export default function create_manifest_data({ config, output, cwd = process.cwd
 					type: 'page',
 					pattern,
 					params,
+					// @ts-ignore
 					path,
+					// @ts-ignore
 					a,
+					// @ts-ignore
 					b
 				});
 			} else {
diff --git a/packages/kit/src/core/node/index.js b/packages/kit/src/core/node/index.js
index de4e68725bdb..1542dc278ee6 100644
--- a/packages/kit/src/core/node/index.js
+++ b/packages/kit/src/core/node/index.js
@@ -9,7 +9,7 @@ export function getRawBody(req) {
 		const h = req.headers;
 
 		if (!h['content-type']) {
-			return fulfil(null);
+			return fulfil('');
 		}
 
 		req.on('error', reject);
@@ -18,7 +18,7 @@ export function getRawBody(req) {
 
 		// https://github.com/jshttp/type-is/blob/c1f4388c71c8a01f79934e68f630ca4a15fffcd6/index.js#L81-L95
 		if (isNaN(length) && h['transfer-encoding'] == null) {
-			return fulfil(null);
+			return fulfil('');
 		}
 
 		let data = new Uint8Array(length || 0);
diff --git a/packages/kit/src/runtime/client/renderer.js b/packages/kit/src/runtime/client/renderer.js
index 926593b8deaa..8f3b9abfa43d 100644
--- a/packages/kit/src/runtime/client/renderer.js
+++ b/packages/kit/src/runtime/client/renderer.js
@@ -34,7 +34,7 @@ function page_store(value) {
 
 /**
  * @param {RequestInfo} resource
- * @param {RequestInit} opts
+ * @param {RequestInit} [opts]
  */
 function initial_fetch(resource, opts) {
 	const url = typeof resource === 'string' ? resource : resource.url;
@@ -82,7 +82,9 @@ export class Renderer {
 
 		/** @type {import('./types').NavigationState} */
 		this.current = {
+			// @ts-ignore
 			page: null,
+			// @ts-ignore
 			session_id: null,
 			branch: []
 		};
@@ -114,7 +116,7 @@ export class Renderer {
 			this.session_id += 1;
 
 			const info = this.router.parse(new URL(location.href));
-			this.update(info, [], true);
+			if (info) this.update(info, [], true);
 		});
 		ready = true;
 	}
@@ -137,12 +139,6 @@ export class Renderer {
 		/** @type {import('./types').NavigationResult | undefined} */
 		let result;
 
-		/** @type {number | undefined} */
-		let new_status;
-
-		/** @type {Error | undefined} new_error */
-		let new_error;
-
 		try {
 			for (let i = 0; i < nodes.length; i += 1) {
 				const is_leaf = i === nodes.length - 1;
@@ -160,8 +156,12 @@ export class Renderer {
 				if (node && node.loaded) {
 					if (node.loaded.error) {
 						if (error) throw node.loaded.error;
-						new_status = node.loaded.status;
-						new_error = node.loaded.error;
+						result = await this._load_error({
+							status: node.loaded.status,
+							error: node.loaded.error,
+							path: page.path,
+							query: page.query
+						});
 					} else if (node.loaded.context) {
 						context = {
 							...context,
@@ -175,14 +175,9 @@ export class Renderer {
 		} catch (e) {
 			if (error) throw e;
 
-			new_status = 500;
-			new_error = e;
-		}
-
-		if (new_error) {
 			result = await this._load_error({
-				status: new_status,
-				error: new_error,
+				status: 500,
+				error: e,
 				path: page.path,
 				query: page.query
 			});
@@ -203,6 +198,7 @@ export class Renderer {
 		dispatchEvent(new CustomEvent('sveltekit:navigation-start'));
 
 		if (this.started) {
+			// @ts-ignore
 			this.stores.navigating.set({
 				from: {
 					path: this.current.page.path,
@@ -269,6 +265,7 @@ export class Renderer {
 		this.loading.promise = null;
 		this.loading.id = null;
 
+		if (!this.router) return;
 		const leaf_node = navigation_result.state.branch[navigation_result.state.branch.length - 1];
 		if (leaf_node && leaf_node.module.router === false) {
 			this.router.disable();
@@ -294,8 +291,8 @@ export class Renderer {
 
 		if (!this.invalidating) {
 			this.invalidating = Promise.resolve().then(async () => {
-				const info = this.router.parse(new URL(location.href));
-				await this.update(info, [], true);
+				const info = this.router && this.router.parse(new URL(location.href));
+				if (info) await this.update(info, [], true);
 
 				this.invalidating = null;
 			});
@@ -330,6 +327,7 @@ export class Renderer {
 	 */
 	async _get_navigation_result(info, no_cache) {
 		if (this.loading.id === info.id) {
+			// @ts-ignore if the id is defined then the promise is too
 			return this.loading.promise;
 		}
 
@@ -338,7 +336,7 @@ export class Renderer {
 
 			// check if endpoint route
 			if (route.length === 1) {
-				return { reload: true };
+				return { reload: true, props: {}, state: this.current };
 			}
 
 			// load code for subsequent routes immediately, if they are as
@@ -399,7 +397,8 @@ export class Renderer {
 		};
 
 		for (let i = 0; i < filtered.length; i += 1) {
-			if (filtered[i].loaded) result.props[`props_${i}`] = await filtered[i].loaded.props;
+			const loaded = filtered[i].loaded;
+			if (loaded) result.props[`props_${i}`] = await loaded.props;
 		}
 
 		if (
@@ -534,7 +533,7 @@ export class Renderer {
 	/**
 	 * @param {import('./types').NavigationCandidate} selected
 	 * @param {boolean} no_cache
-	 * @returns {Promise<import('./types').NavigationResult>}
+	 * @returns {Promise<import('./types').NavigationResult | undefined>} undefined if fallthrough
 	 */
 	async _load({ route, path, query }, no_cache) {
 		const key = `${path}?${query}`;
@@ -545,6 +544,7 @@ export class Renderer {
 		}
 
 		const [pattern, a, b, get_params] = route;
+		// @ts-ignore - the pattern is for the route which we've already matched to this path
 		const params = get_params ? get_params(pattern.exec(path)) : {};
 
 		const changed = this.current.page && {
@@ -610,7 +610,9 @@ export class Renderer {
 
 						if (node.loaded.redirect) {
 							return {
-								redirect: node.loaded.redirect
+								redirect: node.loaded.redirect,
+								props: {},
+								state: this.current
 							};
 						}
 
@@ -651,7 +653,7 @@ export class Renderer {
 								context: node_loaded.context
 							});
 
-							if (error_loaded && error_loaded.loaded.error) {
+							if (error_loaded && error_loaded.loaded && error_loaded.loaded.error) {
 								continue;
 							}
 
@@ -713,7 +715,7 @@ export class Renderer {
 				error,
 				module: await this.fallback[1],
 				page,
-				context: node && node.loaded && node.loaded.context
+				context: (node && node.loaded && node.loaded.context) || {}
 			})
 		];
 
diff --git a/packages/kit/src/runtime/client/types.d.ts b/packages/kit/src/runtime/client/types.d.ts
index 1a5861912b1b..7b78c53ac1a5 100644
--- a/packages/kit/src/runtime/client/types.d.ts
+++ b/packages/kit/src/runtime/client/types.d.ts
@@ -17,13 +17,13 @@ export type NavigationCandidate = {
 export type NavigationResult = {
 	reload?: boolean;
 	redirect?: string;
-	state?: NavigationState;
-	props?: Record<string, any>;
+	state: NavigationState;
+	props: Record<string, any>;
 };
 
 export type BranchNode = {
 	module: CSRComponent;
-	loaded: NormalizedLoadOutput;
+	loaded: NormalizedLoadOutput | null;
 	uses: {
 		params: Set<string>;
 		path: boolean;
diff --git a/packages/kit/src/runtime/load.js b/packages/kit/src/runtime/load.js
index 9f55560eaad2..3e555083ca01 100644
--- a/packages/kit/src/runtime/load.js
+++ b/packages/kit/src/runtime/load.js
@@ -10,7 +10,7 @@ export function normalize(loaded) {
 
 		if (!loaded.error && has_error_status) {
 			return {
-				status,
+				status: status || 500,
 				error: new Error()
 			};
 		}
diff --git a/packages/kit/src/runtime/server/index.js b/packages/kit/src/runtime/server/index.js
index f31955a7045b..24c8cbb47796 100644
--- a/packages/kit/src/runtime/server/index.js
+++ b/packages/kit/src/runtime/server/index.js
@@ -50,8 +50,7 @@ export async function respond(incoming, options, state = {}) {
 						$session: await options.hooks.getSession(request),
 						page_config: { ssr: false, router: true, hydrate: true },
 						status: 200,
-						branch: [],
-						page: null
+						branch: []
 					});
 				}
 
@@ -67,13 +66,13 @@ export async function respond(incoming, options, state = {}) {
 						// inject ETags for 200 responses
 						if (response.status === 200) {
 							if (!/(no-store|immutable)/.test(response.headers['cache-control'])) {
-								const etag = `"${hash(response.body)}"`;
+								const etag = `"${hash(response.body || '')}"`;
 
 								if (request.headers['if-none-match'] === etag) {
 									return {
 										status: 304,
 										headers: {},
-										body: null
+										body: ''
 									};
 								}
 
diff --git a/packages/kit/src/runtime/server/page/load_node.js b/packages/kit/src/runtime/server/page/load_node.js
index 8d024d1b9433..05d34a2daad4 100644
--- a/packages/kit/src/runtime/server/page/load_node.js
+++ b/packages/kit/src/runtime/server/page/load_node.js
@@ -20,7 +20,7 @@ const s = JSON.stringify;
  *   status?: number;
  *   error?: Error;
  * }} opts
- * @returns {Promise<import('./types').Loaded>}
+ * @returns {Promise<import('./types').Loaded | undefined>} undefined for fallthrough
  */
 export async function load_node({
 	request,
diff --git a/packages/kit/src/runtime/server/page/render.js b/packages/kit/src/runtime/server/page/render.js
index 7817eb0f5608..492d302398fc 100644
--- a/packages/kit/src/runtime/server/page/render.js
+++ b/packages/kit/src/runtime/server/page/render.js
@@ -13,8 +13,8 @@ const s = JSON.stringify;
  *   page_config: { hydrate: boolean, router: boolean, ssr: boolean };
  *   status: number;
  *   error?: Error,
- *   branch: Array<import('./types').Loaded> | undefined;
- *   page: import('types/page').Page
+ *   branch?: Array<import('./types').Loaded>;
+ *   page?: import('types/page').Page
  * }} opts
  */
 export async function render_response({
@@ -134,10 +134,10 @@ export async function render_response({
 						.join(',\n\t\t\t\t\t\t')}
 					],
 					page: {
-						host: ${page.host ? s(page.host) : 'location.host'}, // TODO this is redundant
-						path: ${s(page.path)},
-						query: new URLSearchParams(${s(page.query.toString())}),
-						params: ${s(page.params)}
+						host: ${page && page.host ? s(page.host) : 'location.host'}, // TODO this is redundant
+						path: ${s(page && page.path)},
+						query: new URLSearchParams(${page ? s(page.query.toString()) : ''}),
+						params: ${page && s(page.params)}
 					}
 				}` : 'null'}
 			});
diff --git a/packages/kit/src/runtime/server/page/respond.js b/packages/kit/src/runtime/server/page/respond.js
index 86faafca7ec3..c1f7913c74a8 100644
--- a/packages/kit/src/runtime/server/page/respond.js
+++ b/packages/kit/src/runtime/server/page/respond.js
@@ -13,10 +13,11 @@ import { coalesce_to_error } from '../utils.js';
  *   $session: any;
  *   route: import('types/internal').SSRPage;
  * }} opts
- * @returns {Promise<import('types/hooks').ServerResponse>}
+ * @returns {Promise<import('types/hooks').ServerResponse | undefined>}
  */
 export async function respond({ request, options, state, $session, route }) {
 	const match = route.pattern.exec(request.path);
+	// @ts-ignore we already know there's a match
 	const params = route.params(match);
 
 	const page = {
@@ -29,7 +30,7 @@ export async function respond({ request, options, state, $session, route }) {
 	let nodes;
 
 	try {
-		nodes = await Promise.all(route.a.map((id) => id && options.load_component(id)));
+		nodes = await Promise.all(route.a.map((id) => options.load_component(id)));
 	} catch (/** @type {unknown} */ err) {
 		const error = coalesce_to_error(err);
 
@@ -48,9 +49,9 @@ export async function respond({ request, options, state, $session, route }) {
 	const leaf = nodes[nodes.length - 1].module;
 
 	const page_config = {
-		ssr: 'ssr' in leaf ? leaf.ssr : options.ssr,
-		router: 'router' in leaf ? leaf.router : options.router,
-		hydrate: 'hydrate' in leaf ? leaf.hydrate : options.hydrate
+		ssr: 'ssr' in leaf ? !!leaf.ssr : options.ssr,
+		router: 'router' in leaf ? !!leaf.router : options.router,
+		hydrate: 'hydrate' in leaf ? !!leaf.hydrate : options.hydrate
 	};
 
 	if (!leaf.prerender && state.prerender && !state.prerender.all) {
@@ -59,7 +60,7 @@ export async function respond({ request, options, state, $session, route }) {
 		return {
 			status: 204,
 			headers: {},
-			body: null
+			body: ''
 		};
 	}
 
@@ -110,6 +111,8 @@ export async function respond({ request, options, state, $session, route }) {
 
 					if (loaded.loaded.error) {
 						({ status, error } = loaded.loaded);
+					} else {
+						branch.push(loaded);
 					}
 				} catch (/** @type {unknown} */ err) {
 					const e = coalesce_to_error(err);
@@ -134,7 +137,8 @@ export async function respond({ request, options, state, $session, route }) {
 							}
 
 							try {
-								error_loaded = await load_node({
+								// there's no fallthough on an error page, so we know it's not undefined
+								error_loaded = /** @type {import('./types').Loaded} */ (await load_node({
 									request,
 									options,
 									state,
@@ -147,7 +151,7 @@ export async function respond({ request, options, state, $session, route }) {
 									is_error: true,
 									status,
 									error
-								});
+								}));
 
 								if (error_loaded.loaded.error) {
 									continue;
@@ -179,8 +183,6 @@ export async function respond({ request, options, state, $session, route }) {
 				}
 			}
 
-			branch.push(loaded);
-
 			if (loaded && loaded.loaded.context) {
 				// TODO come up with better names for stuff
 				context = {
diff --git a/packages/kit/src/runtime/server/page/respond_with_error.js b/packages/kit/src/runtime/server/page/respond_with_error.js
index 246d24248284..1bdaa0e20117 100644
--- a/packages/kit/src/runtime/server/page/respond_with_error.js
+++ b/packages/kit/src/runtime/server/page/respond_with_error.js
@@ -23,7 +23,8 @@ export async function respond_with_error({ request, options, state, $session, st
 		params: {}
 	};
 
-	const loaded = await load_node({
+	// error pages don't fall through, so we know it's not undefined
+	const loaded = /** @type {import('./types').Loaded} */ (await load_node({
 		request,
 		options,
 		state,
@@ -34,11 +35,11 @@ export async function respond_with_error({ request, options, state, $session, st
 		context: {},
 		is_leaf: false,
 		is_error: false
-	});
+	}));
 
 	const branch = [
 		loaded,
-		await load_node({
+		/** @type {import('./types').Loaded} */ (await load_node({
 			request,
 			options,
 			state,
@@ -51,7 +52,7 @@ export async function respond_with_error({ request, options, state, $session, st
 			is_error: true,
 			status,
 			error
-		})
+		}))
 	];
 
 	try {
diff --git a/packages/kit/tsconfig.json b/packages/kit/tsconfig.json
index 4aa3600f50de..efea64c3cf5e 100644
--- a/packages/kit/tsconfig.json
+++ b/packages/kit/tsconfig.json
@@ -3,11 +3,7 @@
 		"allowJs": true,
 		"checkJs": true,
 		"noEmit": true,
-		"noImplicitAny": true,
-		"alwaysStrict": true,
-		"strictBindCallApply": true,
-		"strictFunctionTypes": true,
-		"noImplicitThis": true,
+		"strict": true,
 		"target": "es2020",
 		"module": "es2020",
 		"moduleResolution": "node",
diff --git a/packages/kit/types/internal.d.ts b/packages/kit/types/internal.d.ts
index a85bb346ebd5..599c481ae1fc 100644
--- a/packages/kit/types/internal.d.ts
+++ b/packages/kit/types/internal.d.ts
@@ -211,7 +211,7 @@ export type BuildData = {
 };
 
 export type NormalizedLoadOutput = {
-	status?: number;
+	status: number;
 	error?: Error;
 	redirect?: string;
 	props?: Record<string, any> | Promise<Record<string, any>>;