Customer data, in marketing technology, is the work of joining an email address, a phone number, a device identifier and a cookie into one person. The joining can happen inside one company, using its own records, or across many companies at once. Joining these signals is called identity resolution.
Why is it needed? Consider a furniture store in Kochi that sells in its showrooms and online. One customer signed up on its website with her email address. Later, she paid at the showroom's billing counter and gave her phone number. She also uses the store's app, which knows her phone only by a device identifier, a code that marks her phone inside the app. Last month, she clicked one of the store's advertisements, and her browser stored a cookie, a small file that marks her browser. To the store, she looks like four different people. Until the four records are joined, the store may send her a welcome offer she has already used, or an advertisement for a sofa she already bought.
The zone has two products. A customer data platform (CDP) joins the records inside one company. It collects what each customer does on the website, in the app and at the store, and keeps one live profile for each person. Some CDPs keep no copy of their own, and work on the data where it already sits. These are called composable CDPs.
An identity graph does the harder job of joining people across companies. It links the devices, emails and addresses of millions of people. With it, an advertiser can recognise its own customer on a news website. Data onboarding uses the graph to find a brand's offline customers online. A data clean room lets two companies compare their customer lists without either seeing the other's names.
All of this depends on first-party data, the data a company collects itself. For years, advertisers also used third-party cookies to follow people across websites. Today, Safari blocks all third-party cookies by default. Firefox blocks the cookies of known tracking companies by default. It also keeps every other third-party cookie separate for each website, so the cookie cannot follow a person to other sites. Chrome, the most used browser in India, still allows third-party cookies, because Google decided in April 2025 to keep them. Privacy law sets limits too. Under India's DPDP Act, a company must have the customer's consent to use personal data for marketing. This duty applies from 13 May 2027. The matched identities are then used to decide who sees which advertisement, often in auctions run by real-time bidding.