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Unknown Cookies that seem like by Optimizely

Tammy 04-13-16

Unknown Cookies that seem like by Optimizely



I found weird cookies today on my website like below:





My company has a strict regulation to use Cookie for secure connection for users, so appearing such unknown cookies without any explanation is pain for us very much.

Could you let me know what they are?


Just in case, the capture if them:


Thank you,


Level 6


Re: Unknown Cookies that seem like by Optimizely

[ Edited ]

Hi Tammy,

Thanks for posting your question here on Optiverse! This is a cookie that Optimizely sets to check what the corresponding top-level domain of the page is (what the highest level domain is that Optimizely can set its cookies on). The name + values are randomly generated and don't have any extra meaning.

In most cases though, these cookies shouldn't appear. Optimizely by default has a list of top-level domains that it checks against to find out where it should set its cookies, but for edge cases the top-level domain isn't in this list. This option can then be turned on an account-level (only for select Enterprise plans) which I'm guessing has been done for you, so that the Optimizely cookies are set on the correct (top-level) domain. They also should only exist temporarily, as they have a very early expiration date. And if you use the JavaScript API to set the cookie domain, that will still take precedence.

I saw you also submitted a support ticket with us. I'll follow-up there in case I can dig into a specific page that you're seeing this on.

Best wishes,