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Browser Storage Quota Inspector

Most browsers grant a single origin a slice of disk — usually a few hundred MB on the low end, up to ~60% of free disk space on Chrome — shared across localStorage, sessionStorage, IndexedDB, Cache Storage, the File System Access API, and Service Worker registrations. This page calls navigator.storage.estimate() for the total and adds up each individual API for a per-bucket breakdown.

Used

—

via storage.estimate()

Quota

—

approx, may grow with disk

Available

—

quota − used

Persisted

—

protected from eviction

0% of quota

Persistence only affects this origin. "Clear all" wipes localStorage, sessionStorage, cookies (this origin only), every IndexedDB database we can list, and every Cache Storage bucket. Use it to start fresh while testing.

Breakdown by API

Bucket	Items	Approx size	Status

Sizes for localStorage/sessionStorage/cookies are measured directly (UTF-16 byte count). IndexedDB and Cache Storage sizes are estimated by serializing each record/response — the engine's on-disk overhead, indexes, and compression are not captured.

Stress test

Write a chunk of data to a bucket and watch the numbers move. The data is keyed under __quota-tester__ so the Clear button can find it.

Bucket Size (KB) Records

What each API stores

localStorage — synchronous string K/V, ~5 MB hard cap per origin in every browser. Survives reloads, cleared when the user clears site data.
sessionStorage — same shape as localStorage but scoped to the tab. Wiped on tab close.
IndexedDB — async object store, structured cloneable values (Blobs, Files, ArrayBuffers OK). Counts against the global quota.
Cache Storage — Request/Response pairs, the storage powering Service Worker offline assets. Also against the global quota.
OPFS (Origin Private File System) — sandboxed filesystem via navigator.storage.getDirectory(). Counts against quota; sizes not walked here (would be slow on large trees).
Cookies — capped at 4 KB each, ~150 cookies per origin in most browsers, doesn't count against storage.estimate().

Quota rules of thumb

Chrome: up to 60% of free disk space, single origin can use up to 60% of that. Eviction is "best-effort" — least-recently-used origins get cleared first.
Firefox: 10% of disk per group of eTLD+1, max 10 GB per origin.
Safari: stricter — 1 GB per origin and a 7-day eviction window for non-persistent storage on sites the user hasn't interacted with recently.
Call navigator.storage.persist() to request persistent storage; if granted, the origin survives quota pressure.