iOS 10.3 Safari cookies won't delete

I've had the same issue with being unable to delete a number of "0 Bytes" cookies on my iPad for a while, but recently an eBay.co.uk cookie of 508KB size began to exhibit the same behaviour - at which point I "snapped", enough is enough! I found a solution, however it's a little long-winded and requires a Mac:

1. Connect the iOS device to a Mac and create a backup using iTunes
2. Open the backup using an explorer/editor tool such as iBackupBot (I was a little dubious about using this at first, but it was signed by a registered developer and did not require installation nor did it ask for a password input at any stage, so pretty safe)
3. Navigate to the folder "User App Files > com.apple.mobilesafari > Library > Webkit > Website Data"
4. Delete all files and folders in the enclosed IndexedDB folder - this is where the 508KB of eBay data seemed to be
5. Delete all files and folders in the enclosed WebSQL folder - where all the other "0 Bytes" cookies are stored. I was amazed there were even cookies in here which didn't show up in the Website Data view in Settings. Mine had a whole trove of cookies from argos.co.uk, ebay.co.uk, and uk.farnell.com amongst others.
6. Restore the backup to your iOS device using iTunes

This was sucessful for me on both my iPad Pro and iPhone SE - both on iOS 10.3.3. I can't confirm if it will work for iOS 11 devices, but from what I've read many people have found the cookie problem to be fixed in 11.1.2.

Full reset of my iPad worked and now the 0 byte / persistent cookies are gone and new cookies can readily be deleted. I visit one of the websites that had previously caused problems and the issue did not recur. What did surprise me however was the number of cookies generated by visiting a single website but at least they can now be deleted.

I found a partial solution: turn off Javascript before clearing website data. I went from a few screens full of zombie cookies to 4. Like all cookies, they'll accumulate again over time when you turn Javascript back on, but the ones stashed in Javascript won't don't come back unbidden.

Out on the interwebs I learned these zombies stuff themselves away in various places in the OS, with Javascript being a favorite. HTML5 caches are another. Those stowaways can monitor if they've been deleted from the normal web cache and repropagate. I had already tried deleting with WiFi turned off, and the zombies came back, so clearly they were stored somewhere on the device.

In this light these zombie cookies are not a bug on Apple's part: they are an intentional end run around the operating system's privacy protocols.

I'm most annoyed at the big companies using these things: ebay and Michael's (crafts) are two that I cannot shake still.

Yes, it appears to be!

I've just updated to iOS 11, tried a couple sites that were dropping persistent cookies, and they no longer persist.

"Prevent Cross-Site Tracking" in Safari Settings is on by default.

Apple has sounded serious about improving privacy, and so far, so good.

I confirm , iOS 11.2 correct this bug 💁-1F3FC;♂☺

The issue is that these companies – perhaps more likely the ad agency or networks each spends with – are dropping a cookie that intentionally defeats Apple's intent and users' desire. BTW, I have one zombie that retains some data (it's more than zero bytes).

The issue is twofold: first is the subterfuge. Nobody, IMHO, can really complain about the cookies and caches that help our internet experience to work, as long as they play by known rules. That's not what zombie cookies are. The second is that, while the files contain no data, the file names are data. They defeat the user's intent to wipe internet history from the browser.

There's a class action lawsuit again Verizon's ad agency for dropping zombie cookies; it advanced just a couple weeks ago. The offense happened and suit was initiated before net privacy rules were revoked.

Experience with updating seems variable.

For me the zombie cookies disappeared when I first updated to iOS 11 on both my iPhone 7 and first generation iPad Pro. (I think things were fixed on my Mac after Sierra.) Now with the latest (11.2.1) the zombies still go away.

Both devices were updated using iTunes wired to my Mac. (No WiFi update with the Mac; no Over-the-Air update: perhaps those are important variables.) I don’t think I did anything special, but there were zombie cookies before the updates and now when I clear cookies none remain or come back.

Did you by any chance look at the Safari web data after updating the iPad but before using Safari?

It's a complete guess on my part, but I'm wondering if the zombie cookies you see now are all holdovers stashed in a user file that did not get overwritten in the update. In other words, the issue does not persist going forward, but the past zombies don't go away.

You may be stuck going nucler, resetting your device and doing a fresh install. (Hopefully recovering user data won't bring back the zombies.)

Did you try the trick I found earlier, turning off Javascript temporarily before clearing web data?

It was a reset of all data and settings and not a restore from backup.

Only thing that has ever worked for me is a complete reinstall - wiping then setting up as a new iphone. Of course, the cookies can reappear.

Even in iOS 11.1 the cookies are still there

Plus I just discovered that they look like 0 kb but actually they are not 0 kb. The folder hosting the cookie-data shows 0 kb

but inside the folder there are so many files that go from 4 kb to 33 kb, total of 450 kb. 0 is written on the url-name of the folder

Example

https_mail.google.com_0

What is even worse is that I thought I had only one persistent cookie but actually there are 3 more and they don't show in Safari/Advanced/Website Data

I was able to see those using an app on my Mac that let you browse your backup.

The cookie I have shows 0 but actually is 528 kb and what is worse is adding files almost every day.

The files are 3 kinds

.wal-shm

.db

.wal

and there are several of them, google has 96, total of 2.1 Mb and it's one of the invisible cookies

Awful!!!

Please elaborate on why you think your iPhone is unfit for purpose due to the existence of a small bug in clearing cookies, which has subsequently been fixed in the latest version.

It's worth noting that the existence of this bug has only been revealed due to its exploitation by companies attempting track your browsing history at all costs using ethically questionable methods, IE: ever cookies, supercookies etc.

iOS 11.2.1: 'Remove all website data' is fixed, all data is deleted including so-called 0-byte cookies.

For me it was already resolved with iOS 11.2.6 and didn't come back with 11.3

I wonder if there’s something different on the iPad. I just went to weather.com and, while the visit to one single page earned me 23 cookies, they all went away and stayed away when cleared. Javascript on the entire time; all settings under “privacy and security” turned on except for block all.

Hmm, my iPhone is good after the same test.

The issue could still be third party advertisers dropping zombie cookies on behalf of these sites. We don’t all see the same ads on a given page, so perhaps I’m just lucky so far.