What is the c cookie?
The c cookie belongs to the .casalemedia.com domain, owned by Casale Media, the company operating Index Exchange — one of the largest programmatic advertising exchanges worldwide. It is not set directly by the site a visitor browses, but by an advertising intermediary (SSP/ad exchange) when the page loads an ad tag or takes part in a real-time bidding (RTB) auction.
In practice, this cookie can appear on any site that serves ads through platforms connected to Index Exchange, even if the site owner has no direct relationship with Casale Media — the integration usually happens through a third-party ad platform (SSP, DSP, or ad network).
What data it stores
The cookie stores a unique, randomly generated identifier used to recognize the visitor's browser on later visits. The exact value format is not publicly documented and may vary; it typically does not contain directly identifiable data such as a name or email address, but it is still considered an online identifier under GDPR.
Data linked to this identifier is sent to Casale Media/Index Exchange servers and may be shared with other advertising partners involved in the programmatic bidding chain, for ad matching and measurement purposes.
What it is used for
The main purpose of the cookie is to identify and track visitors within the programmatic advertising ecosystem, enabling:
- participation in RTB auctions for the site's ad slots;
- building an approximate interest profile based on browsing history across partner sites;
- measuring ad campaign performance and limiting repeated display of the same ad (frequency capping).
For the site owner, the indirect benefit is better monetization of ad inventory, since targeted ads tend to attract higher bids from advertisers.
Does it require consent?
The „c” cookie falls under the marketing/advertising category. Since it is not strictly necessary for the site to function, setting it requires the visitor's prior consent under Law 506/2004 (Romania's transposition of the ePrivacy Directive) and GDPR principles governing processing via online identifiers.
Site owners must disclose this cookie (or the ad tag that generates it) in their cookie policy, classify it correctly under the marketing category in the consent banner, and ensure the related script does not run before the visitor gives explicit consent.
How to block or delete c
A visitor can delete or block this cookie from browser settings (Chrome, Firefox, Edge, Safari — privacy/cookie section), by clearing cookies for the .casalemedia.com domain, or by using an anti-tracking browser extension. They can also opt out of the marketing category directly from the site's consent banner, if granular choices are offered.
For site owners, blocking the cookie automatically before consent is the job of the CMP in use. A platform like CookieFix can prevent scripts that trigger Casale Media/Index Exchange cookies from running until the visitor explicitly accepts the marketing category, avoiding premature setting of these identifiers.
Frequently asked questions
No, it is not a virus or malware — it is an advertising tracking cookie used for RTB auctions and ad targeting. It can raise privacy concerns, which is why it requires consent.
It usually appears indirectly, through an ad platform (SSP/DSP) or ad network connected to Index Exchange, which loads Casale Media tags for programmatic auctions.
The typical duration is about 1 year from the last time it was set or updated, similar to most identifier cookies used in programmatic advertising.
Yes. As a marketing cookie requiring consent under GDPR and ePrivacy rules, it should be explicitly listed with its purpose, duration, and provider (Casale Media/Index Exchange).