Advertising without third-party cookies

The cross-site tracking cookie has been unreliable for years. Most browsers block it by default, consent rates cap it further, and the practical consequence arrived long before any deadline.

What actually broke

Three functions depended on it: recognising the same person across different websites, attributing a conversion to an advertisement seen elsewhere, and capping frequency across sites.

All three now work partially or not at all, which is why reported conversions have fallen and reported cost per acquisition has risen in accounts where nothing else changed.

The four replacements

None is a complete substitute. Together they cover most of what was lost, differently.

First-party data is the durable answer

Data you collect directly, with consent, in your own relationship with the customer. Email addresses, purchase history, preferences, account behaviour.

It is unaffected by browser policy, it works across channels, and it belongs to you. The businesses least disrupted by the whole transition are those that already had a customer list.

Building it takes years, which is the argument for starting now rather than when the next mechanism breaks.

Contextual targeting works again

Placing advertising by the content of the page rather than the identity of the reader. It was the standard before behavioural targeting and it never stopped working.

Modern contextual tools analyse page meaning rather than matching keywords, which addresses the crude blocking problems of earlier systems.

For brand and awareness objectives it performs comparably to behavioural targeting at lower cost and with no privacy exposure.

Modelled conversions

Platforms estimate the conversions they cannot observe, using the ones they can. That is statistically reasonable and it means your reported numbers are partly estimates.

Practical consequence: treat platform conversion figures as directional, and validate with holdout tests rather than trusting the decimal places.

What to do

1. Build first-party data deliberately, with a genuine value exchange and clean consent.
2. Implement server-side measurement, which recovers signal within the rules.
3. Shift display budget towards contextual, particularly for brand objectives.
4. Use holdout tests to validate what the platforms report.
5. Reduce reliance on cross-site retargeting, which is the function that degraded most.

The consent reality

Whatever the technical mechanism, processing personal data for advertising requires a lawful basis and usually consent. Systems designed to work around a refusal are unlawful, and the technical route makes no difference to that.