sveltejs/kit · warning

Failed to initialize SvelteKit cache:

Error message

Failed to initialize SvelteKit cache:

What it means

The client-side remote-function prerender module initializes a Cache Storage bucket ('sveltekit:' caches) in an IIFE; if any Cache API operation fails, it logs 'Failed to initialize SvelteKit cache:' with the error via console.warn and continues without caching. This can happen in browsers/environments where caches or Cache API operations are unavailable or fail (private mode, storage quota, non-secure context).

Source

Thrown at packages/kit/src/runtime/client/remote-functions/prerender.svelte.js:29

// Initialize Cache API for prerender functions
const CACHE_NAME = __SVELTEKIT_DEV__ ? `sveltekit:${Date.now()}` : `sveltekit:${version}`;
/** @type {Cache | undefined} */
let prerender_cache;

const prerender_cache_ready = (async () => {
	if (typeof caches !== 'undefined') {
		try {
			prerender_cache = await caches.open(CACHE_NAME);

			// Clean up old cache versions
			const cache_names = await caches.keys();
			for (const cache_name of cache_names) {
				if (cache_name.startsWith('sveltekit:') && cache_name !== CACHE_NAME) {
					await caches.delete(cache_name);
				}
			}
		} catch (error) {
			console.warn('Failed to initialize SvelteKit cache:', error);
		}
	}
})();

/**
 * @param {string} url
 * @param {string} encoded
 */
function put(url, encoded) {
	return /** @type {Cache} */ (prerender_cache)
		.put(
			url,
			// We need to create a new response because the original response is already consumed
			new Response(encoded, {
				headers: {
					'Content-Type': 'application/json'
				}
			})

View on GitHub (pinned to 03f1687fe6)

Solutions

1. Serve the app over HTTPS (or localhost) so the Cache API is available.
2. Disable private-browsing/site-data blocking for the origin during testing.
3. Ignore the warning if caching is non-essential — the app degrades gracefully.

// detect Cache API availability before relying on cached remote data
if (typeof caches === 'undefined' || !('open' in caches)) {
  console.info('Cache Storage unavailable — running uncached');
}

const cache_api_available = () =>
  typeof window !== 'undefined' && 'caches' in window && window.isSecureContext;

try {
  const cache = await caches.open('sveltekit:my-data');
} catch (error) {
  console.warn('Cache unavailable, continuing without cache:', error);
}

When it happens

Trigger: Loading a SvelteKit app using remote functions/prerendered data caching in a browser context where window.caches is missing, Cache Storage access is blocked, or caches.delete/open throws (Safari private browsing, embedded webviews, quota errors).

Common situations: Testing in private/incognito mode, in a non-HTTPS origin (cache API requires secure context), or in webviews with storage disabled; users see the warning in console but the app still works, just without the cache.

Related errors

• ${prerendered.error}
• Preloading data for ${intent.url.pathname} failed with the f
• The next HMR update will cause the page to reload

AI-assisted analysis of sveltejs/kit@03f1687fe6 (2026-09-02). Data as JSON: /api/errors/0e9516e8fff0fbd4. Report an issue: GitHub.