What is the cid cookie?
The cid cookie is set by Adform, one of Europe's major ad-tech providers, offering an ad server, demand-side platform (DSP) and data management platform (DMP) used by agencies and brands to serve and measure online advertising campaigns.
It typically appears on a website when that site runs Adform ads, an Adform conversion pixel, or a tag loaded through a partner relying on Adform's infrastructure (for example, retargeting or programmatic advertising integrations). The associated domain is usually .adform.net.
What data it stores
„cid” most likely stores a unique identifier generated for the visitor's browser (a client/cookie ID used to correlate advertising events). The exact value format is not documented in detail publicly and may vary.
The data is sent to Adform's servers (under the .adform.net domain), where it is linked to that identifier's history of ad impressions, clicks and, where applicable, conversions.
What it is used for
For Adform, the cookie allows recognizing the same visitor across repeat visits, which underpins behavioral targeting, frequency capping (limiting how often an ad is shown) and attributing conversions to a specific campaign.
For the website operator, this type of cookie indirectly supports advertising monetization or performance reporting for marketing campaigns run through Adform, but it does not provide functionality required for the page to display correctly.
Does it require consent?
In CookieFix's classification, „cid” falls under the marketing category (advertising/tracking). Under the GDPR (Regulation 2016/679) and the ePrivacy Directive (transposed in Romania via Law 506/2004), this type of cookie is not strictly necessary and requires the visitor's prior, explicit and informed consent before being set.
The website operator should declare the cookie in the cookie policy, list it under the marketing category in the consent banner, and ensure the Adform script that generates it does not run before the visitor has opted in to that category.
How to block or delete cid
A visitor can delete or block this cookie from browser settings (for example, clearing cookies for .adform.net or blocking third-party cookies), or can decline the marketing category in a consent banner.
- From browser settings: manually delete cookies from the Adform domain or disable third-party cookies.
- Via anti-tracking or ad-blocking browser extensions.
- By withdrawing consent through a cookie preference panel, where the site provides one.
For site operators, a CMP like CookieFix can automatically block the Adform script (and therefore prevent the „cid” cookie from being set) until the visitor explicitly accepts the marketing category, avoiding placement without consent.
Frequently asked questions
It is not a virus or malware, but it is a tracking cookie used for targeted advertising, which is why data protection law treats it as privacy-sensitive and requires consent.
Its typical duration is around 2 months, after which it expires automatically, though it may be renewed if the visitor interacts again with an Adform-served ad.
Yes, since it is classified as marketing/advertising, it requires the user's prior consent under GDPR and ePrivacy rules, as it is not a strictly necessary cookie.
You cannot directly remove a cookie set by a third party like Adform except by preventing their script from loading; the correct approach is blocking the Adform script until consent is given, via a CMP, rather than manually deleting the cookie repeatedly.