DocumentationAnalyticsImplementation Guide

cookieDomainPeriods

Last update: Thu Mar 07 2024 00:00:00 GMT+0000 (Coordinated Universal Time)

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AppMeasurement determines its cookie location by looking at the domain and domain suffix. For domains like example.com, AppMeasurement sets cookies in the correct location. However, for other domains like example.co.uk, AppMeasurement can mistakenly set cookies on co.uk. Most browsers reject cookies set on this invalid domain, causing issues with visitor identification.

The cookieDomainPeriods variable helps AppMeasurement determine where Analytics cookies are set by calling out that the domain suffix has an extra period in it. This variable allows AppMeasurement to accommodate the extra period in the domain suffix and set cookies in the right location.

  • For domains like example.com or www.example.com, this variable does not need to be set. If needed, you can set this variable to "2".
  • For domains like example.co.uk or www.example.co.jp, set this variable to "3".
IMPORTANT
Do not take subdomains into account for this variable. For example, do not set cookieDomainPeriods on the example URL store.toys.example.com. AppMeasurement by default recognizes that cookies should be stored on example.com, even on URLs with many subdomains.

Only when you are using the legacy Adobe Analytics visitor identification (instead of the recommended Experience Cloud Identity service), the implicit or explicit configuration of cookieDomainPeriods can have implications on how visitors are identified, depending on whether third-party cookies are blocked or not.

The following table illustrates four possible scenarios.

Scenario
cookieDomainPeriods configuration is …
Third-party cookies are blocked?
Result when using legacy Adobe Analytics visitor identification service
1
Correct
No
Visitors are identified with an s_vi cookie, set server-side.
2
Correct
Yes
Visitors are identified with a fallback s_fid cookie, set client-side (first-party page domain).
3
Incorrect
No
Visitors are identified with fallback identifier based on combination of user agent and IP-address.
AppMeasurement is forced to set cookies as third-party cookies.
The s_vi cookie is possibly set when cookieDomainPeriods is not transmitted properly.
4
Incorrect
Yes
Visitors are identified with fallback identifier based on combination of user agent and IP-address.
AppMeasurement is forced to set cookies as third-party cookies which are blocked, so no cookies are set.
CAUTION
You might have inadvertently configured cookieDomainPeriods incorrect (leaving it at its default value of "2") while using domains like example.co.uk. This implicit incorrect configuration results that you are identifying visitors following scenario 3 or 4.
AppMeasurement release 2.26.x or later configures cookieDomainPeriods automatically with the correct value so only scenarios 1 or 2 are possible. When you update to AppMeasurement release 2.26.x or later, while currently identifiying visitors incorrectly (scenario 3 or 4), the update has major implications.
  • Visitor identifiers are being reset and visitors will appear as new visitors. There will be no way to tie new activity to the previous visitor identifier.
  • Cookies are set (such as for link tracking or activity map, e.g.s_sq cookie), resulting in sudden differences in reporting.
While correctly configuring cookieDomainPeriods will improve AppMeasurement and Analytics functionality, it is recommended to assess whether you are affected by the changes resulting from upgrading your AppMeasurement library.
See Analytics Cookies for more information about the cookies AppMeasurement uses.

The Web SDK can determine the correct cookie storage domain without this variable.

Domain Periods is a field under the Cookies accordion when configuring the Adobe Analytics extension.

  1. Log in to Adobe Experience Platform Data Collection using your AdobeID credentials.
  2. Click the desired tag property.
  3. Go to the Extensions tab, then click the Configure button under Adobe Analytics.
  4. Expand the Cookies accordion, which reveals the Domain Periods field.

Set this field to 3 only on domains containing a period in its suffix. Otherwise this field can be left blank.

You can set the cookieDomainPeriods variable in the AppMeasurement Javascript library or in the custom code editor of the Analytics extension.

The cookieDomainPeriods variable is a string that is typically set to "3", only on domains that contain a period in its suffix. Its default value is "2", which accommodates most domains.

// Manually set cookieDomainPeriods for domains with a period in its suffix, such as www.example.co.uk
s.cookieDomainPeriods = "3";

// Detect if a URL has a domain suffix with an extra period, and set s.cookieDomainPeriods automatically
document.URL.indexOf(".co.") > 0 ? s.cookieDomainPeriods = "3" : s.cookieDomainPeriods = "2";
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