this post was submitted on 18 Aug 2024
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Firefox

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I've enabled "Delete cookies and site data when Firefox is closed" but while all cookies gets deleted, some random site data does not. Are my settings wrong, is this a bug, and what even is that data?

Additional Info: I use RFP, want to keep browsing history and site settings. Thank you very much.

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[–] [email protected] 9 points 2 months ago (1 children)

That could simply be the cookies.txt file with no content whatsoever.

[–] [email protected] 5 points 2 months ago* (last edited 2 months ago)

Firefox stores cookies in a DB file called cookies.sqlite, i just cleared cookies on a fresh new Firefox profile and the file is 524.3kB. A text dump of the file has four lines of text that describe the structure of the cookie database and that's it. No actual content.

[–] [email protected] 8 points 2 months ago

Sounds like it's localStorage. But I'd expect that to be covered by "site data" in that option.

It's a bit like cookies, but just for one site. Some think they can avoid cookie consent banners with localStorage.

Firefox has a page on the topic.

[–] [email protected] 5 points 2 months ago (1 children)

What is the data it's keeping? 25-100 bytes doesn't seem like there's anything actually there.

[–] [email protected] 2 points 2 months ago* (last edited 2 months ago) (2 children)

8 bytes is enough to store 18,446,744,073,709,551,616 (18 quintillion) different values, more than enough space for a fingerprint ID. The size of the data shouldn't factor into the potential threat.

[–] [email protected] 4 points 2 months ago (1 children)

Oh for sure, I just wonder if the size being the same on 2 of them is a result of Firefox storing some default data there on cleanup by accident.

[–] [email protected] 2 points 2 months ago

Oh, I get it now! In my sleep deprived state I missed that two of them had the same size. That seems like a reasonable guess, I'm just paranoid about cookies :P

[–] [email protected] 2 points 2 months ago (1 children)

Except the actual content is very likely boilerplate stuff.

[–] [email protected] 7 points 2 months ago

My point still stands. The size of data says nothing about its contents. If OP is concerned about this from a security or privacy perspective, you shouldn't be writing them off because it's only 100 bytes.