Retargeting is a digital advertising technique that serves ads specifically to users who have previously visited a website or interacted with a brand online, with the goal of bringing them back to complete a desired action such as a purchase or sign-up.
Most visitors leave a website without converting on their first visit. Retargeting addresses this by keeping a brand visible to those users as they browse other websites, social media platforms, or apps. Because the audience has already demonstrated some level of interest, retargeted ads tend to achieve higher conversion rates than standard display advertising aimed at cold audiences.
Pixel-Based Retargeting
The most common form of retargeting relies on a small piece of JavaScript code placed on a website, commonly called a retargeting pixel or tracking pixel. When a visitor lands on a page, the pixel fires and drops a cookie in the user's browser. Advertising platforms - such as Google Ads or Meta Ads - read that cookie and use it to identify the user when they appear elsewhere on the web, triggering the relevant ad. Pixel-based retargeting is highly automated and works in near real-time, making it well suited for e-commerce sites that want to follow up with users who viewed a product or abandoned a shopping cart.
List-Based Retargeting
An alternative approach uses first-party data that a business already holds, typically a list of email addresses collected through sign-ups, purchases, or CRM systems. This list is uploaded directly to an advertising platform, which attempts to match those addresses to its own registered users. List-based retargeting offers more control over the audience, since marketers can segment by customer lifecycle stage or purchase history, but it depends on the quality and size of the existing data set and does not capture anonymous visitors the way pixel-based methods do.
Retargeting vs. Remarketing
Retargeting is often used interchangeably with remarketing, and the two terms describe closely related strategies. In practice, remarketing is the broader concept - encompassing email campaigns sent to lapsed customers, for example - while retargeting more specifically refers to paid display or social advertising served to past visitors. Google has historically used the term remarketing to describe what most of the industry calls retargeting, which contributes to the overlap.
Privacy Considerations
As third-party cookies are phased out by major browsers, pixel-based retargeting is undergoing significant change. Advertisers are increasingly relying on first-party data strategies, server-side tracking, and platform-native audience tools to maintain targeting accuracy. Understanding both pixel-based and list-based approaches gives marketers the flexibility to adapt as the privacy landscape continues to evolve.