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Chrome extension storage explained: where your data actually lives
Local stays on your device. Sync follows your Google account. FeedUndo uses only chrome.storage.local — so your last 10 viewed Reddit posts never leave the machine you viewed them on.
TL;DR: chrome.storage.local = on-device, inside your Chrome profile. chrome.storage.sync = synced via your Google account — but only if the extension explicitly uses it. FeedUndo uses only local. Nothing syncs. Nothing is visible to other sites.
The two storages Chrome offers extensions
Extensions choose which bucket to use. The difference matters for privacy, quota, and what happens when you switch devices.
| Storage area | Scope | Quota | Syncs to Google? | Cleared when? |
|---|---|---|---|---|
| chrome.storage.local | This device only | ~10 MB | No | Extension uninstalled |
| chrome.storage.sync | All devices on same Google account | ~100 KB (quota'd, throttled) | Yes | Stays until cleared |
| chrome.storage.session | Memory only | ~10 MB | No | Browser closes |
Quotas are Chrome defaults and approximate — extensions define their own payload shape within them. FeedUndo stores only title + URL + subreddit + thumbnail key for the last 10 — well under local limits. It never writes to sync or session.
What is stored — and what isn't
Only the last 10 viewport hits after install: post title, subreddit, URL, thumbnail key. No Reddit username, no OAuth token, no cookies, no browsing history outside reddit.com.
// write (content script after IntersectionObserver fires)
await chrome.storage.local.set({ feedUndoHistory: last10 });
// read (popup)
const { feedUndoHistory } = await chrome.storage.local.get("feedUndoHistory");
Inspect it yourself: chrome://extensions → FeedUndo → Details → Inspect views → Application → Storage → Local Storage. No network request happens on read.
IntersectionObserver + MutationObserver on shreddit-post that enters the viewport while you're on reddit.com after install. It cannot look back before install.
Extension popup → click any row to reopen. Also inspectable at chrome://extensions → Inspect views. Recover a lost post →
Free tier keeps 10. After a manual founder review of a public recovery story containing https://feedundo.pages.dev, the cap is removed — still local, just unlimited.
What leaves your device (almost nothing)
A hashed install ID and event name (e.g. popup_opened, post_reopened). No URLs, no titles. You can decline at first open and change anytime in the popup. See how privacy works in detail.
Only if you choose to unlock unlimited: the public Reddit URL you post that includes https://feedundo.pages.dev. A founder opens it manually. No post-content scrape, no subreddit API crawl.
That's it. No OAuth, no Reddit login connected, no content sync. Compare with Save vs Upvote vs Hide — which list is which for what Reddit itself remembers.
What happens if you uninstall or clear data
Chrome removes the extension's chrome.storage.local area. There's no cloud backup to restore from — that's the privacy tradeoff. Reinstalling starts from zero (only posts viewed after reinstall).
The Clear button wipes the local last-10. Unlimited after approval is still local — just the cap removed. No server copy remains.
How to verify it yourself
- Open chrome://extensions → find FeedUndo → Details.
- Under Inspect views, click service worker or popup to open DevTools.
- In DevTools → Application → Storage → Local Storage → chrome-extension://… — you'll see feedUndoHistory and nothing else synced.
- Open Network tab and click around the popup — no Reddit content leaves the device.
Where does chrome.storage.local keep extension data?
In the browser profile on your device, inside Chrome's extension storage area. It is not a website cookie and is not accessible to other sites or extensions.
Does chrome.storage.local sync to Google or another device?
No. Only chrome.storage.sync syncs via your Google account and only if the extension uses it. FeedUndo uses only chrome.storage.local, so your last 10 posts stay on the device where you viewed them.
Can the extension developer see my local storage?
No. Local storage is on your device and never sent to FeedUndo's server. Only anonymous install events (if you opt in) and a public URL you voluntarily submit for unlock ever reach the server.
What happens to my history if I uninstall FeedUndo?
Uninstalling the extension removes its chrome.storage.local data. You can also clear the last 10 from the popup. There is no cloud backup to restore from — that's the privacy tradeoff.
How is FeedUndo different from browser history?
Browser history only records pages you opened. FeedUndo records posts that crossed the viewport on reddit.com after install, even if you never clicked them — then lets you reopen them locally. Both are local; neither recovers posts from before install.
Your history stays where you left it.
Last 10 posts, on your device, in chrome.storage.local. No sync. No cloud. See the full policy or install in two minutes.
Chrome manual beta + Firefox on AMO · feedundo.pages.dev