diff --git a/.changeset/four-lamps-walk.md b/.changeset/four-lamps-walk.md
new file mode 100644
index 000000000000..d2abb0ef2b2a
--- /dev/null
+++ b/.changeset/four-lamps-walk.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+[breaking] Disallow error status codes outside 400-599
diff --git a/packages/kit/src/exports/index.js b/packages/kit/src/exports/index.js
index b0ae3243e0aa..0ad15b8d92fa 100644
--- a/packages/kit/src/exports/index.js
+++ b/packages/kit/src/exports/index.js
@@ -8,12 +8,22 @@ import { HttpError, Redirect, ValidationError } from '../runtime/control.js';
  * @param {any} message
  */
 export function error(status, message) {
+	if (
+		(!__SVELTEKIT_BROWSER__ || __SVELTEKIT_DEV__) &&
+		(isNaN(status) || status < 400 || status > 599)
+	) {
+		throw new Error(`HTTP error status codes must be between 400 and 599 — ${status} is invalid`);
+	}
+
 	return new HttpError(status, message);
 }
 
 /** @type {import('@sveltejs/kit').redirect} */
 export function redirect(status, location) {
-	if (isNaN(status) || status < 300 || status > 308) {
+	if (
+		(!__SVELTEKIT_BROWSER__ || __SVELTEKIT_DEV__) &&
+		(isNaN(status) || status < 300 || status > 308)
+	) {
 		throw new Error('Invalid status code');
 	}
 
diff --git a/packages/kit/src/runtime/control.js b/packages/kit/src/runtime/control.js
index 2bcf963985a2..16ea65416416 100644
--- a/packages/kit/src/runtime/control.js
+++ b/packages/kit/src/runtime/control.js
@@ -43,56 +43,3 @@ export class ValidationError {
 		this.data = data;
 	}
 }
-
-/**
- * Creates an `HttpError` object with an HTTP status code and an optional message.
- * This object, if thrown during request handling, will cause SvelteKit to
- * return an error response without invoking `handleError`
- * @param {number} status
- * @param {string | undefined} [message]
- */
-export function error(status, message) {
-	return new HttpError(status, message);
-}
-
-/**
- * Creates a `Redirect` object. If thrown during request handling, SvelteKit will
- * return a redirect response.
- * @param {300 | 301 | 302 | 303 | 304 | 305 | 306 | 307 | 308} status
- * @param {string} location
- */
-export function redirect(status, location) {
-	if (isNaN(status) || status < 300 || status > 308) {
-		throw new Error('Invalid status code');
-	}
-
-	return new Redirect(status, location);
-}
-
-/**
- * Generates a JSON `Response` object from the supplied data.
- * @param {any} data
- * @param {ResponseInit} [init]
- */
-export function json(data, init) {
-	// TODO deprecate this in favour of `Response.json` when it's
-	// more widely supported
-	const headers = new Headers(init?.headers);
-	if (!headers.has('content-type')) {
-		headers.set('content-type', 'application/json');
-	}
-
-	return new Response(JSON.stringify(data), {
-		...init,
-		headers
-	});
-}
-
-/**
- * Generates a `ValidationError` object.
- * @param {number} status
- * @param {Record<string, any> | undefined} [data]
- */
-export function invalid(status, data) {
-	return new ValidationError(status, data);
-}
diff --git a/packages/kit/test/apps/basics/test/test.js b/packages/kit/test/apps/basics/test/test.js
index be47fcb68a93..8678d1b1a6b6 100644
--- a/packages/kit/test/apps/basics/test/test.js
+++ b/packages/kit/test/apps/basics/test/test.js
@@ -1295,28 +1295,32 @@ test.describe('Redirects', () => {
 
 		await clicknav('[href="/redirect/missing-status/a"]');
 
+		const message = process.env.DEV || !javaScriptEnabled ? 'Invalid status code' : 'Redirect loop';
+
 		expect(page.url()).toBe(`${baseURL}/redirect/missing-status/a`);
 		expect(await page.textContent('h1')).toBe('500');
 		expect(await page.textContent('#message')).toBe(
-			'This is your custom error page saying: "Invalid status code"'
+			`This is your custom error page saying: "${message}"`
 		);
 
 		if (!javaScriptEnabled) {
 			// handleError is not invoked for client-side navigation
 			const lines = read_errors('/redirect/missing-status/a').stack.split('\n');
-			expect(lines[0]).toBe('Error: Invalid status code');
+			expect(lines[0]).toBe(`Error: ${message}`);
 		}
 	});
 
-	test('errors on invalid status', async ({ baseURL, page, clicknav }) => {
+	test('errors on invalid status', async ({ baseURL, page, clicknav, javaScriptEnabled }) => {
 		await page.goto('/redirect');
 
 		await clicknav('[href="/redirect/missing-status/b"]');
 
+		const message = process.env.DEV || !javaScriptEnabled ? 'Invalid status code' : 'Redirect loop';
+
 		expect(page.url()).toBe(`${baseURL}/redirect/missing-status/b`);
 		expect(await page.textContent('h1')).toBe('500');
 		expect(await page.textContent('#message')).toBe(
-			'This is your custom error page saying: "Invalid status code"'
+			`This is your custom error page saying: "${message}"`
 		);
 	});