Retargeting: definition, mechanics and GDPR
Updated on February 22, 2026
Quick definition
Retargeting is an advertising technique that targets users who have already interacted with your website or app, in order to encourage them to return and complete an action (purchase, sign-up, quote request). Retargeting relies on identifying visitors via third-party cookies or identifiers to serve them personalised ads on other sites or social networks.
How it works
Retargeting works in two phases.
Tracking phase: a pixel or JavaScript tag placed on the advertiser's site identifies visitors and adds them to an audience list (e.g. "visitors of the product page who did not purchase").
Activation phase: when these visitors browse elsewhere, the advertiser's DSP recognises the identifier and displays a personalised ad.
There are several forms of retargeting:
- Display: banners on third-party sites
- Social: Facebook, Instagram, LinkedIn ads
- Email: if the email address is known
- Search: Google Ads targeting previous visitors
- Dynamic: ads automatically generated with the products viewed
Retargeting performance is generally superior to cold-audience campaigns: click-through rates 10x higher and lower cost per conversion. However, effectiveness drops quickly with saturation (over-exposure) and is heavily impacted by the blocking of third-party cookies.
Why it matters
Retargeting is one of the most cost-effective levers in performance marketing because it targets users already familiar with the brand and at an advanced stage of the buying journey.
In a well-structured conversion funnel, retargeting acts as a safety net to maximise the return on investment of other acquisition channels.
However, its effectiveness is increasingly threatened by the progressive disappearance of third-party cookies in modern browsers (Firefox, Safari, and soon Chrome).
How to improve or use it
- 1Segment your audiences by intent level (homepage visitors vs checkout vs abandoned carts) and tailor the message to each segment.
- 2Set strict frequency capping (3 to 5 maximum exposures per user over 30 days).
- 3Systematically exclude already-converted customers.
- 4Test variable retargeting windows (7, 14, 30 days) to identify the optimal window.
- 5Obtain GDPR consent before placing retargeting cookies.
With Sublim
Sublim lets you accurately identify the visitor segments most suited to retargeting (e.g. visitors who reached step 3 of a funnel without converting) without third-party cookies. These segments can be exported to your ad platforms via the Sublim API, for first-party data retargeting campaigns that are more durable and GDPR-compliant.
Frequently asked questions
Is retargeting legal in France?
Yes, retargeting is legal provided that explicit consent is obtained from the user before placing advertising cookies, in line with GDPR and CNIL recommendations. The lack of valid consent can expose the advertiser to significant administrative penalties.
Does retargeting still work without third-party cookies?
Traditional retargeting based on third-party cookies is losing effectiveness with browsers such as Firefox and Safari that block them. Alternatives include: first-party retargeting (via owned cookie or email), retargeting via walled gardens (Facebook Pixel, Google Tag, LinkedIn Insight Tag) and clean rooms for partner data.
What is the optimal duration of a retargeting window?
The optimal duration depends on the buying cycle. For impulse-purchase products (fashion, cosmetics), 7 to 14 days is enough. For products requiring longer consideration (software, cars, real estate), 30 to 90 day windows are more appropriate. It is advisable to test several windows and analyse the conversion rate by time cohort.
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