What is the demdex cookie?
demdex is an HTTP cookie associated with Adobe Audience Manager (AAM), Adobe's data management platform (DMP) used for audience segmentation and personalized advertising. It is operated by third-party vendors integrating Adobe Experience Cloud into their sites.
The cookie typically appears when a site integrates Adobe scripts for marketing, audience analytics, or data synchronization with other advertising platforms (data management platform / partner DSPs).
What data it stores
demdex stores a unique identifier associated with the visitor, generated by Adobe Audience Manager to recognize them on return visits and across other sites within the same Adobe ecosystem. The exact value format varies and is not publicly documented in detail.
The cookie is placed on the .demdex.net domain, an Adobe-specific domain used for identifier synchronization between advertising platforms (cookie syncing / ID matching), with data sent to Adobe's servers.
What it is used for
For Adobe, demdex is used to build audience segments based on browsing behavior, allowing advertising agencies and brands to target users with similar profiles across multiple websites.
For the site owner, the cookie supports remarketing campaigns, ad performance measurement, and sharing audience data with other tools in the digital marketing stack.
Does it require consent?
demdex is classified as a marketing/tracking cookie. Under the ePrivacy Directive (2002/58/EC) and GDPR (Regulation 2016/679), this type of cookie requires the visitor's explicit, prior consent before being set, since it involves tracking online behavior and building advertising profiles.
Site owners must disclose this cookie in their cookie policy, correctly classify it under the "marketing" category in the consent banner, and ensure the Adobe script does not run before the visitor gives consent.
How to block or delete demdex
Visitors can delete or block demdex via browser cookie settings, use anti-tracking extensions, or disable third-party cookies. Adobe also offers opt-out options at the Adobe Experience Cloud account level for some products.
- Manual deletion from browser privacy settings
- Blocking third-party cookies in the browser
- Ad-tracker blocking extensions
On the site side, a CMP such as CookieFix can automatically block the Adobe Audience Manager script until the visitor gives consent for the marketing category, preventing the demdex cookie from being set prematurely.
Frequently asked questions
It's a marketing cookie set by Adobe Audience Manager, used to identify visitors for targeted advertising and audience segmentation.
It's not malicious, but it is a tracking cookie that collects behavioral data for advertising profiling, which is why it requires consent under GDPR.
It typically lasts around 6 months, after which it expires automatically unless the visitor returns to sites that renew it.
Yes, since it's a marketing cookie, it should only be set after the visitor gives explicit consent through the cookie banner.