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Tuesday 20th April 2021

What Are Flash Cookies?


Flash cookies (also known as Local Shared Objects) are set within an embedded Adobe Flash movie on a website page. They can store a significant amount of data compared to a normal HTTP cookie (around 100Kb default* as opposed to 4Kb), and they do not (at the time of writing) show up in the list of cookies when using the techniques described in Can I control Cookies?

* This can be set to any size with user permission.

In order to check (and control) Flash cookies you will need to use the Adobe Flash Player Settings Manager. You can do this by right-clicking on a Flash movie and selecting Global Settings from the pop-up menu or by visiting the Adobe Flash Player Settings Manager web page.

If you are a website owner, these Local Shared Objects fall under the same legislation as normal HTTP cookies, and the same rules apply!

Watch out for the Zombies!

No Zombies here!

Some of you may have come across a situation where you have deleted your traditional HTTP cookies, yet somehow a website still remembers you. This can be achieved using Flash cookies by some of the more unscrupulous developers out there, and has been termed 'Zombie Cookies' due to the fact that they can keep on recreating themselves unless you do something about it.

How it works...
When you delete your HTTP cookies via your browser, a Flash cookie can be used to automatically recreate it (if needed) the next time you start up your browser. This can also be accomplished with the recent HTML5 storage techniques.

How to stop it...
Open the Adobe Flash Player Settings Manager as described above, and either delete the offending object, or block all objects, depending on your needs and preferences.

Now that you know what Flash Cookies are, let's take a look at the privacy law and how it affects them.

Can I tell if my website is using Flash Cookies?

At the time of writing, only the Safari 5.x web browser allows you to view/manage/delete Flash Cookies without the use of extensions or additional plug-ins.

Safari Go to Edit > Preferences > Privacy > Details...

You will see 'Plug-ins' listed under the domain. You also have the option to remove the data (this will also clear the cache and any cookies that may have been set).