What does scientific evidence say about the cookieless future — both the revenue impact and whether privacy technologies actually protect users?

Removing third-party cookies cuts publisher revenue ~29–60%, and "privacy-preserving" alternatives like Topics API still leak: combined with fingerprinting, re-identification reaches 57% after 15 weeks.

Revenue impact:

• Gu et al. (June 2025), "Can Privacy Technologies Replace Cookies?" — full third-party-cookie removal causes an average 29.1% revenue loss for content publishers
• Criteo market analysis — publishers lose on average 60% of programmatic ad revenue; first-party-data strategies recover only 15–25%

Re-identification risk of "privacy" tech (Beugin & McDaniel, 2023):

• Topics API re-identification looks low at 0.4% per week — but accumulates over time
• Combination attacks: linking Topics data with browser fingerprinting raises re-identification to 57% after 15 weeks (and rising further to roughly 75% as more data accumulates)

The key implication: isolated privacy technologies offer insufficient protection. Only comprehensive Privacy-by-Design approaches are effective long-term — a single mechanism (Topics, CHIPS) bolted on is not enough.