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Deleting Flash Cookies

I’m A Super: What if there was a type of cookie that could:

Count me in the set of people who were previously unaware that such cookies existed.  As to deletion, I prefer a more direct approach:

rm -rf     ~/.macromedia/Flash_Player/#SharedObjects/*/*
chmod 0500 ~/.macromedia/Flash_Player/#SharedObjects/*
rm -rf     ~/.macromedia/Flash_Player/*
chmod 0500 ~/.macromedia/Flash_Player/

Inspired by Dan Scott.  Also available as a firefox plugin.

This is fixable, see

Feedback appreciated.

Posted by Julian Reschke at

Feedback: enabling responsible plugin authors to do the right thing is not something I would consider a complete fix.  A complete fix would look something like a sandbox.  Until this is addressed, I would suggest that the documentation for private browsing is both misleading and incomplete.

Posted by Sam Ruby at

Posting such a script is dangerous!

$> cd ~/.macromedia/Flash_Player/#SharedObjects/*
bash: cd: /Users/peritus/.macromedia/Flash_Player/#SharedObjects/*: No such file or directory
$> rm -rf * # <-- ouch!

Posted by Peritus at

Modified the script to be less dangerous.  Thanks!

Posted by Sam Ruby at

There’s a nice study of Flash cookie usage—including using Flash cookies to “respawn” HTTP cookies—here: [link]

Posted by Ryan Shaw at

The quoted blog source ("What if there was a type of cookie that could...") is incorrectly sourced to “Dave Brooks”, while the link is correct. The proper Author is “I’m A Super”. :)

Although the author was incorrectly cited, I do appreciate you taking the time to have a proper link. Excellent script, by the way.


I’m a

Posted by I'm A Super at

Sorry about that.  Attribution corrected.  FWIW, I drew the wrong conclusion from this page.

Posted by Sam Ruby at

Another important “feature” of Flash cookies is that they are cross-browser. That is to say that even when you navigate with two different browsers from the same machine, the Flash information is shared:

Posted by Alexandre at

Howdy, longtime issue... Macromedia Flash Player has offered greater-than-cookie-sized local storage since 2002. Never really got onto the radar, although there’s a yearly scare campaign on it. (First such was United Virtualities' PIE in 2005, if you’d like to check on it.)

The initial interface was tricky, because browsers had no such capabilities, and a SWF could be sized on the page smaller than its control dialog. That’s why there’s a special UI to inspect your own local storage.

These days Player hooks up with the “Private Browsing” sessions available in many browsers, and we hope to work with browser vendors to further integrate its control into their interfaces.

The issue is complicated, however... some banks and other institutions use local storage as a device confirmation method... meanwhile search query “adobe ftc cookie respawning” shows an aspect of non-consensual use. Things must work for all.

Titles generally aren’t as juicy as the scares on the webcam, however.... ;-)


Posted by John Dowdell at

Hi John.  I appreciate that this might be complicated for others, but I will simply state that the issue is not complicated for me.

Nor is my intent to scare anyone, merely to educate.

Posted by Sam Ruby at

On OS X:

rm -rf     ~/Library/Preferences/Macromedia/Flash\ Player/#SharedObjects/*/*
chmod 0500 ~/Library/Preferences/Macromedia/Flash\ Player/#SharedObjects/*
rm -rf     ~/Library/Preferences/Macromedia/Flash\ Player/*
chmod 0500 ~/Library/Preferences/Macromedia/Flash\ Player/
Posted by Bob Aman at

Flash cookies και πως να τα ξεφορτωθείτε.

Φανταστείτε ένα cookie που: Παραμένει στον υπολογιστή σας για απεριόριστο χρόνο Αποθηκεύει τουλάχιστον 100kb δεδομένων και δεν έχει ανώτατο όριο μεγέθους Δεν εντοπίζεται από το browser σας Αποστέλλει δεδομένα για τα site που έχετε επισκεφθεί, χωρίς...

Excerpt from at


my understanding is that, given the latest versions of Firefox and Flash, “private browsing” will indeed do the expected thing with respect to Flash cookies. See for the relevant NPAPI extension).

Also notice that there are similar concerns with HTML5 local storage. See, for instance,

Best regards, Julian

Posted by Julian Reschke at

Thanks Sam. I’ve been using the various panels of the Flash Player Settings Manager to deal with Flash cookies, but found it not very convenient. Your approach looks hopeful.

Here’s the link to the 6 panels at the Flash Player Settings Manager:


Posted by Gary Lewis at

The steps in this post make the Flash plugin (10,0,45,2 on Ubuntu 10.04) crash on certain SWF files, like the D8 videos embedded in this post.  At least with Chromium and Firefox 3.6.4 it doesn’t take down the browser...

Posted by Matt Brubeck at

With the chmod commands, does this prevent flash cookies from being stored going forward? I haven’t seen any cookies show up since I ran these commands.

Posted by Shane at

I did something more radical but which is also less likely to cause problems:

( crontab -l ; printf '0\t1\t*\t*\t*\t/bin/rm -rf %s/.macromedia\n' "$HOME" ) | crontab -
Posted by Aristotle Pagaltzis at

Sam Ruby: Deleting Flash Cookies

Keep Flash from setting cookies on Mac OS X...

Excerpt from Delicious/niclindh at


Changing directory permissions will break certain sites that appear to rely on writing a cookie they can then immediately read back (various video sharing sites for example).

My preferred solution is a cron job:

$ crontab -l 
*/10 * * * * rm -rf "${HOME}/Library/Preferences/Macromedia/Flash Player"
Posted by dw at

Links for 2010-06-04 []

Sun Bug ID: 6822370 ReentrantReadWriteLock: threads hung when there are no threads holding onto the lock TIL about -XX:+UseMembar Deleting Flash Cookies Excellent tip...

Excerpt from Sounds From The Dungeon at

[from chillnc] Sam Ruby: Deleting Flash Cookies


Excerpt from Delicious/url/515c97418547098c9f52c200a0349b51 at

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