What is the tt_pixel_session_index cookie?
tt_pixel_session_index is a cookie set by the TikTok Pixel script, which advertisers and site owners embed to measure the performance of ad campaigns run on TikTok. The cookie typically appears as soon as the TikTok Pixel loads on a page, regardless of whether the visitor has ever used TikTok itself.
It is set under the visited site's own domain (a first-party cookie from the browser's perspective), but the data it helps collect is sent to TikTok/ByteDance for processing and ad attribution.
What data it stores
The cookie stores a numeric identifier used internally by the pixel to mark the order or index of events within a browsing session (for example, which event/page in the current session is being logged). It generally does not contain directly identifying information like a name or email, but it is part of a broader set of TikTok cookies (alongside others used for browser/device identification) that can collectively contribute to a behavioral profile of the visitor.
The exact value format may vary and is not publicly documented in detail by TikTok. Collected data is transmitted to TikTok's servers, which may involve transfers outside the European Economic Area.
What it is used for
For TikTok, this cookie helps correlate on-site events with browsing sessions to build conversion reports and optimize ad delivery. For the site owner, it enables measuring the results of paid TikTok Ads campaigns (for example, how many purchases came from a specific campaign) and building retargeting audiences.
Does it require consent?
tt_pixel_session_index is classified as a marketing/advertising cookie. Under Law 506/2004 (transposing the ePrivacy Directive) and the GDPR, this type of cookie cannot be set before the visitor's explicit consent is obtained.
- Site owners must list the cookie in their cookie policy under the "marketing" category.
- The TikTok Pixel should only load after the visitor accepts the marketing category in the consent banner.
- Missing prior consent can be sanctioned by the Romanian data protection authority (ANSPDCP).
How to block or delete tt_pixel_session_index
A visitor can delete this cookie from browser settings (Chrome, Firefox, Edge, Safari) via the site's cookie management section, or use private/incognito mode or anti-tracking extensions to prevent it from being set.
For site owners, blocking needs to happen technically, not just in a policy document: the TikTok Pixel script must stay inactive until consent is given. A CMP like CookieFix can do this automatically, intercepting and blocking the TikTok script from loading until the visitor grants consent for the marketing category.
Frequently asked questions
It's set by the TikTok Pixel script embedded on a website that runs TikTok ads, even though it technically appears as a cookie belonging to that site's own domain.
Yes, as a marketing/advertising tracking cookie, it requires the visitor's prior explicit consent under Romanian law and the GDPR.
It's a session cookie, meaning it's automatically deleted when the browser is closed.
The TikTok Pixel script should not load, so tt_pixel_session_index won't be set, meaning the visitor's activity won't be linked to TikTok ad campaigns.