Cookies and the Experience Cloud ID Service
The ID service uses your organization ID, the Experience Cloud AMCV cookie, and a demdex cookie to create and store unique, persistent identifiers for your site visitors. These cookies let the ID service track visitors across your different domains and enable data sharing among different Experience Cloud solutions.
Understanding ID Service cookies
The ID service relies on the AMCV, AMCVS, and demdex cookies to function properly. These cookies are just files that store data used by the ID service. These ID service cookies are not dangerous, malicious, or different from other first- or third-party cookies stored by a website or service in a browser, following the same rules that govern other first- and third-party cookies. Refer to the following sections below for more information about cookies used by the ID service.
What the ID Service cookies can do
- Set and store a unique ID for your site visitors (the MID).
- Persist this unique ID so the ID service can collect and share data with other Experience Cloud solutions.
- Track users across your domains. However, this requires that you own those other domains and have ID service code deployed on them.
What the ID Service ookies cannot do
- Store, transmit, or execute computer viruses.
- Access or store personally identifiable information (PII) like your email address.
- Control computer hardware or software.
- Make computers unstable or cause performance problems.
- Track users on sites that do not use the ID service.
AMCV cookie
The following attributes of the cookie set by the ID service.
Name
The AMCV cookie name follows the syntax AMCV_<variable name>@AdobeOrg. In the name, the <variable name> elements are placeholders for part of your Experience Cloud organization ID. This ID is passed in to the DCS by the Visitor.getInstance function in the ID service code.
A fully formed cookie name would look similar to this:
AMCV_1FD6776A524453CC0A490D44%40AdobeOrg
Contents
The AMCV cookie contains the Experience Cloud visitor ID or MID. The MID is stored in a key-value pair that follows this syntax, mid|<Experience Cloud ID>.
A fully formed key-value pair would look similar to this:
mid|20265673158980419722735089753036633573
This persistent identifier enables cross-solution data sharing.
Domain
The AMCV cookie is set in the first-party domain of a browser. This means it is set in the domain of the site currently visited by a user. As such, ID service code and other Experience Cloud code libraries can read the MID stored in the AMCV cookie.
However, because the AMCV cookie is set in the first-party domain, it cannot be used to track and identify users across different domains. Instead, the ID service relies on the organization ID and the demdex ID to return the correct MID when a site visitor navigates to a different domain.
AMCVS cookie
Name
The AMCVS cookie name follows the syntax AMCVS_####@AdobeOrg. In the name, the #### elements are placeholders for part of your Experience Cloud organization ID. This ID is passed in to the DCS by theVisitor.getInstance function in the ID service code.
A fully formed cookie name would look similar to this:
AMCVS_1FD6776A524453CC0A490D44%40AdobeOrg
Contents
The AMCVS cookie serves as a flag indicating that the session has been initialized. Its value is always `1` and discontinues when the session has ended.
Domain
The AMCVS cookie is set in the first-party domain of a browser. This means it is set in the domain of the site currently visited by a user.
Demdex cookie
The following table lists and defines some important attributes of the demdex cookie.
| Attribute | Description |
|---|---|
|
Name |
The cookie name is "demdex." |
|
Contents |
The demdex cookie contains the demdex ID, which is generated by the DCS. |
|
Domain |
The demdex cookie is set in the third-party, demdex.net domain in the browser. This domain is separate from the site currently visited by a user. Unlike the first-party, AMCV cookie, the demdex cookie and ID persists across different domains. The demdex ID and your organization ID are the common values that allows the ID service to return and identify a site visitor with the right visitor ID. |
For related information, see Understanding Calls to the Demdex Domain.
s_ecid cookie
The following table lists and defines some important attributes of the s_ecid cookie.
| Attribute | Description |
|---|---|
| Information Stored | Contains a copy of the Experience Cloud ID (ECID) or MID. The MID is stored in a key-value pair that follows this syntax, s_ecid=MCMID|<ECID> |
| Expiration | 2 years |
| Usage | This cookie is set by the customer's domain after the AMCV cookie is set by the client. The purpose of this cookie is to allow persistent ID tracking in the 1^st^ party state and is used as a reference ID if the AMCV cookie has expired. Check AMCV cookie here for more details. |
| Location | CNAME customers only. Not applicable for 3^rd^party scenarios. Cookie is stored on your domain, the same domain used by CNAME and your Analytics image request. |
| Size | 45 bytes |
Generating the Experience Cloud ID
The Experience Cloud ID (MID) is derived mathematically from your organization ID and the demdex ID. As long as these IDs remain constant, generating the right MID for a specific user is simply a math problem. With the same organization ID and demdex ID you get the same MID value every time. This allows the ID service to track visitors across domains that you control and have configured with ID service code.
The ID service starts to create a MID as your page loads. During this process, code provided by the visitorAPI.js code library sends your organization ID in an event call to the ID service. The ID service creates and returns the MID and a demdex ID in the AMCV and demdex cookies respectively.
Next steps
See How the Experience Cloud ID Service requests and sets IDs.