What is the IDSYNC cookie?
This cookie is set by Yahoo to track and recognize users across multiple websites for identity resolution, cookie syncing, and serving targeted advertising.
Table of Contents
About IDSYNC
| Vendor | Yahoo |
|---|---|
| Cookie Domain | .yahoo.com |
| Category Category The functional category of the technology, such as Web Analytics or Social Media. Learn more | Advertising & Paid Media |
| Consent Category Consent Category The consent category this cookie most commonly falls under across sites we scan, normalized into four standard categories. Learn more | Targeting & Advertising |
| Prevalence | Very Common |
| Popularity Popularity Popularity is calculated from our dataset of 4.5B+ cookies analyzed across hundreds of millions of web pages. Learn more | Found on 13.6% of scanned pages |
| Expiration Type | Timestamp |
| Expiration Duration | 30 days |
| Party Type Party Type Whether the cookie is first-party or third-party. Learn more | 3rd-Party |
| Risk Level Risk Level Rates how sensitive the data stored by this cookie is (High, Medium, or Low) based on data classification and distribution. Learn more | High |
| Vendor Privacy Policy | https://legal.yahoo.com/ie/en/yahoo/privacy/cookies/index.html |
| Vendor Website | https://www.yahoo.com |
What is the purpose of IDSYNC?
The IDSYNC cookie is a persistent third-party tracking identifier set by Yahoo (formerly operating as Verizon Media / Oath acquired by Yahoo in 2021) on analytics.yahoo.com. Its primary function is identity resolution and cookie synchronization across the open web. Through Yahoo's UPS (Unified Profile Service) cookie-sync endpoints, the cookie enables Yahoo to recognize users across disparate sites and match Yahoo's identifier with those of third-party advertising partners, supporting the Yahoo DSP (Demand-Side Platform) and the Yahoo ConnectID identity graph in compiling pseudonymous user profiles and tracking ad exposure.
This continuous flow of identity data is leveraged to optimize programmatic ad bidding, deliver personalized behavioral advertising, and measure marketing campaign effectiveness. The value of the cookie typically consists of a proprietary identifier (often paired/encoded values such as 19b9~2sxu) unique to the user's browser.
What are the Privacy Risks of IDSYNC?
Risk Level: High
This cookie operates as a cross-site tracker that aggregates user browsing behavior across the open web to build advertising profiles. It actively participates in cookie syncing, meaning pseudonymous user identifiers are shared with multiple third-party ad-tech platforms to facilitate identity resolution and real-time programmatic ad bidding, which can lead to data sharing with third parties. Given the cross-site tracking and identifier-sharing nature of the technology, a High risk level is appropriate.
How to Remove IDSYNC from a Website
To remove the IDSYNC cookie, website administrators must locate and remove all Yahoo advertising, analytics, and cookie-sync tags (such as Yahoo Analytics, Yahoo ConnectID, or Yahoo DSP pixel tags that call ups.analytics.yahoo.com / opus.analytics.yahoo.com) from the site's codebase. If these tags are deployed through a Tag Management System (TMS) or a Customer Data Platform (CDP), the administrator can disable or delete the corresponding tag, or adjust its firing rules so the Yahoo pixel no longer loads. This cookie is an integral part of Yahoo's advertising/identity-sync technology and cannot be disabled independently while Yahoo's tags are allowed to execute; the only way for the site operator to stop it being set is to remove the Yahoo tag/service entirely. If a specific Yahoo integration must remain but the cookie behavior needs adjusting, the operator should contact Yahoo to review account-level configuration options.