Personalize by synchronizing cookie data across devices

You can personalize recommendations by using tracking cookies on more than one computer, smartphone, or tablet.

Because cookies are stored locally on your visitor's device, it is difficult to track and use the information in cookies that are stored on difference devices. For example, a visitor accesses your site from their work computer. The next day, they return by using a mobile device. The cookie data on the work computer is not available to generate personalized recommendations on the mobile device. When they return by using their work computer, the cookie data on the mobile device is not available to generate personalized recommendations on the work computer.

To address this limitation, Digital Recommendations can track the information in your visitor's cookies across multiple devices.

To accomplish this, Digital Recommendations associates the personalization data from your visitor's device to their registration ID. When the user visits your website from a device on which they logged in using their registration ID, Digital Recommendations is able to associate activities that are captured and stored in the Digital Analytics database to that registration ID. When your visitor returns to your site by using another device on which they logged in using their registration ID, the data from the second device is also stored in the database. When the user returns to your website from either device, all data in the database is added to the local cookie and is now available to generate personalized recommendations on either device.

To enable this capability, you need to contact your IBM® representative. You also need to decide how to configure the opt-in requirement. Opt-in configuration determines whether visitors to your site are opted in or opted out by default and affects how you use the opt-in indicator on calls to the cmSetRegId function. The cmSetRegId function accepts an opt-in indicator, but the indicator is only required if the visitor's opt-in state is not the default. Your choices are shown in the following table:

Table 1. Opt-in Options
Option	Description
Mandatory	Select Mandatory opt-in to have visitors opted out by default if no opt-in indicator is specified on the cmSetRegId call. To opt-out a visitor, set the opt-in indicator on each call to `cmSetRegId` to false or leave blank. To opt-in a visitor, set the opt-in indicator on each call to `cmSetRegId` to true. See Synchronize cookie function.
Default	Select Default opt-in to have visitors opted in by default if no opt-in indicator is specified on the cmSetRegId call. To opt-out a visitor, set the opt-in indicator on each call to `cmSetRegId` to false. To opt-in a visitor, set the opt-in indicator on each call to `cmSetRegId` to true or leave blank.

The ability to synchronize cookie data has the following limitations:

The database is updated nightly, so user data from multiple devices is not available until the next day. For example, a user visits your site during the day from a notebook computer. That evening, they return to your site by using a tablet. Any personalization data that is collected on the notebook computer is not available on the tablet. However, if they return to your site by using the tablet the following day, the personalization data from the notebook computer is available on the tablet.
Data from a cookie is only loaded in the database from a device in which the user logged in with their registration ID. If they never logged in from a device, the server cannot collect the data from the cookie on that device. For example, a user browses your site from their work computer on which they never logged in with their registration ID. The next day, they visit your site from their home computer, on which they logged in with their registration ID. The data that is collected on their work computer is not available on their home computer for generating personalized recommendations.