What is the _rdt_uuid cookie?
_rdt_uuid is an HTTP cookie set by Reddit, usually through the Reddit Pixel (Reddit Ads Conversion Tracking) script embedded on sites that run Reddit advertising campaigns or want to measure their performance.
The cookie appears on a site once the owner has installed Reddit's tracking code (pixel or conversions API) for remarketing or conversion reporting — it is not set on a plain visit without that script.
What data it stores
_rdt_uuid stores a unique identifier generated for the visitor's browser, which Reddit uses to link visits on that site to an anonymous user profile within its advertising ecosystem.
The exact value format is not publicly documented in detail by Reddit and may vary. The collected data is sent to Reddit's servers (domains such as reddit.com or redditstatic.com), where it is matched with events like page views, clicks, or conversions.
What it is used for
For Reddit, this cookie enables conversion attribution for Reddit Ads campaigns — determining whether a user who saw or clicked a Reddit ad later completed an action on the advertiser's site (purchase, sign-up, etc.).
For the site owner, it underpins Reddit Ads performance reporting, ad budget optimization, and building remarketing audiences.
Does it require consent?
Under CookieFix's classification, _rdt_uuid falls into the marketing category (advertising/tracking). Because it involves tracking user behavior for advertising purposes, setting it requires the visitor's prior consent under Romania's Law 506/2004 (transposing the ePrivacy Directive) and GDPR data processing principles.
- The site owner must list the cookie in the cookie policy, including provider, purpose, and duration.
- The Reddit Pixel script must not load before the visitor opts into the marketing category.
- Rejecting consent must be as easy as accepting it (per ANSPDCP guidance).
How to block or delete _rdt_uuid
A visitor can delete or block _rdt_uuid from browser settings (Chrome, Firefox, Safari, Edge — per-site cookie management), use private/incognito mode, or install ad-tracker blocking extensions.
For site owners, blocking must happen at the technical level, not just in a policy document: the Reddit Pixel script needs to stay inactive until explicit consent is given. A consent platform like CookieFix can automatically block this script from loading until the visitor accepts the marketing category, preventing the cookie from being set prematurely.
Frequently asked questions
It doesn't contain sensitive data by itself, but it is used for cross-site advertising tracking, which is why it requires consent under GDPR/ePrivacy.
Its typical duration is about 3 months, after which it expires automatically unless renewed by a new visit with the pixel active.
Yes, any site loading the Reddit Pixel script should disclose the cookie, its provider (Reddit), purpose (marketing/advertising), and duration in its cookie policy.
Campaigns can still run, but conversion attribution and automatic ad optimization become less accurate without the data this cookie collects.