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Flash cookies know where you’ve been

I had not heard of Flash cookies until Fernando Bermejo’s Berkman talk last week. Now he’s inaugurated his new blog (well, it’s his second post) with a posting about a new study. Fernando writes:

the white paper concludes “that companies making inappropriate or irresponsible use of the Flash technology are very likely asking for trouble (and potentially putting the rest of the online industry at risk of additional government regulation)”. As for [end users], flash cookies are characterized as “super-cookies which are dramatically more resilient than cookies due to their implementation and a general lack of knowledge about their existence among consumer”.

To remove Flash cookies – which have some peacetime uses – go here.

6 Responses to “Flash cookies know where you’ve been”

  1. in some ways cookies serve an import role in maintaining a website but over use or inappropriate use is troubling … especially when the general public’s understanding of them is almost non-existant

  2. flash cookies are almost exclusively used to track user behavior for advertiser profiling and hardly ever for practicalities like your shopping cart data or remembering your logged in since that is what normal, and rather harmless, cookies are for. this is because only flash cookies allow companies to track users across domains and usually only ad networks (with ads on multiple sites) have any use for that kind of functionality.

    There is a simple remedy and that is blocking flash completely, if your on mac ClickToFlash is a very user friendly implementation for Safari that allows you to control which content you still want to load (youtube movies for instance) with the click of a button:

  3. “because only flash cookies allow companies to track users across domains….”

    No, that’s not correct.


  4. I guess it depends on how you look at it. if your flash based ad is displayed on a 100 different websites from the same ad server the flash movie is still ‘on the same domain’ but you can collect data on multiple sites. If you know which sites your ad will be showed on you can even set the flash security settings so that you can talk to other flash movies on different domains. The local movies would be allowed access to the shared non local movie. Things are definitely improving with each new flash player version (see: ) but there are still some ways to use this that not everybody might be comfortable with.

  5. Try out: For yet another tracking method.

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