Cookie & Storage Support Checker
Check which storage APIs your browser supports: cookies, localStorage, sessionStorage, IndexedDB.
How to use this tool
- Open this page — it runs instantly in your browser, no signup or install.
- Allow any permission prompt if asked; everything stays on your device.
- Use the on-screen controls — results update live.
Check which storage APIs your browser supports: cookies, localStorage, sessionStorage, IndexedDB.
How it works
The Cookie and Storage Support Checker tests four storage mechanisms that web applications rely on: cookies, localStorage, sessionStorage, and IndexedDB. For each one it attempts a small write-read-delete operation and reports whether the operation succeeded, failed, or is unsupported.
Cookies are the oldest form of browser storage and are used for session tokens and preferences. localStorage persists data after the browser closes. sessionStorage lasts only for the current tab session. IndexedDB is a client-side database for larger structured data.
This tool is useful when a web application is behaving unexpectedly — for example, losing login state on every page load (cookies may be blocked) or failing to cache data (localStorage may be disabled by a privacy setting or private browsing mode).
All tests run locally in your browser. No data is sent to a server and the test values written during the check are immediately deleted.
Worked example
Diagnose why a web app keeps logging you out
- Open the Storage Checker in the same browser where the app is misbehaving.
- Check whether cookies show as 'supported and working'.
- If cookies are blocked, the app cannot store your session token.
- Check browser cookie settings and ensure the site is not in a blocked list.
- Reload the Storage Checker to confirm cookies now pass, then retry the app.
Identified that cookies were blocked (common in strict privacy mode), explaining why the app could not maintain login sessions.
Common mistakes to avoid
- Assuming a 'supported' result means unlimited storage is available — browsers impose per-origin storage quotas that apps can exceed.
- Running the check in a private window and concluding that storage is broken globally — private mode intentionally restricts some storage APIs.
- Checking storage support in one browser and drawing conclusions about a different browser where the user is actually experiencing the problem.
Key terms
- localStorage
- A browser storage API that persists key-value string data indefinitely across browser sessions for a given origin, with no expiry date.
- sessionStorage
- A browser storage API that stores key-value data for the lifetime of the current tab or window; data is cleared when the tab is closed.
- IndexedDB
- A low-level browser API for storing large amounts of structured data, including files and blobs, with support for transactions and indexes.
Frequently asked questions
- Why is localStorage blocked?
- Browsers block localStorage in third-party iframes and when the user has set 'Block all cookies'. Private/incognito mode may also restrict it.
- What is the storage quota?
- localStorage is typically limited to 5-10 MB per origin. IndexedDB can store much larger amounts, up to a percentage of available disk space.