When Half Your Traffic Isn’t Human, Retargeting Breaks

Marketing has always run on a simple assumption: a click is a person. A cart addition is desire. A newsletter signup is curiosity. Strip that assumption away and a large chunk of the digital marketing stack starts behaving like a psychology experiment with contaminated participants.

According to reporting by Digiday, automated agents and bots now account for more than half of all web requests, per Cloudflare data. For publishers, that is mostly a headache. For advertisers, it is splitting the room: some brands are courting AI traffic, others are rebuilding their media plans to keep it out.

The brands rolling out the welcome mat

Chad Keller, co-founder of the direct-to-consumer pillow brand Mellow Sleep, told Digiday the company is “less interested in blocking automated traffic than in classifying it,” adding that AI assistants are already sending visitors who convert several times better than the site average. British retailer John Lewis has watched AI agentic searches climb from 0.3% to 2.5% of all web visits in a year, Reuters reported, and is deliberately shaping its web properties to attract more of them.

That is a meaningful signal. An AI assistant arriving on your product page is usually the end of a considered research journey, not the beginning of an idle scroll. The referral is pre-qualified. Blocking it wholesale, as Keller argues, costs more than it saves.

The brands paying for ghosts

The other half of the story is uglier. Mallory Beck, vp of client services at Lighthouse Creative, told Digiday that bot activity inflates impressions and conversions, muddies lookalike audiences and burns through frequency caps. In other words, it doesn’t just waste money, it corrupts the data you use to decide where money goes next.

David Dweck, president at media agency GoFish, said e-commerce clients saw bot traffic rise roughly 80% year over year. Retargeting took the hit: budgets were funnelled towards “users” that were bots, cost-per-acquisition briefly spiked, and performance degraded from Q4 last year into this one. Worse, AI agents can add items to carts and sign up to newsletters — behaviours that older bot filters treat as proof of humanity.

GoFish’s response was to tighten retargeting parameters, which pushed average CPMs up by around 20%. Others gave up on the tactic entirely. Nola Ladd, brand media supervisor at Collective Measures, said the bot surge was “the final nail in the coffin” for retargeting at one client, which moved spend into retail media and social. Megan Herling of LERMA/ noted that bots are only part of the story — privacy updates and data opt-outs have been shrinking retargeting scale for years.

The psychology problem underneath

Retargeting was always a behavioural bet: a visit signals interest, so repeat the message until intent converts. That bet only works if the underlying behaviour is human. Once machines can imitate the cheap signals — pageviews, bounces, cart adds — the cheap signals stop meaning anything.

Beck’s advice is the right frame: get pickier about what counts as a meaningful signal. Think of it as a signal hierarchy, from weakest to strongest:

• Ambient: impressions, pageviews, bounces — now largely uninterpretable
• Ambiguous: cart adds, newsletter signups — increasingly imitable by AI agents
• Costly: logged-in sessions, repeat visits, payment attempts, direct enquiries
• Owned: first-party data, CRM records, loyalty behaviour

Costly signals are hard to fake because faking them requires effort or money. That is exactly why they carry information — the same reason a warranty or a slow-built brand reputation persuades.

What to do this quarter

Audit which conversion events feed your bidding algorithms and demote anything a script could perform. Insist on pre-bid verification and inclusion lists, as Mediassociates’ Tim Lathrop recommends. Shift weight towards first-party data — Ladd’s phrasing, “first party data is king,” is not a slogan but a survival plan. And classify AI agent traffic rather than banning it; it may be your best-converting cohort.

The brands that win here won’t be the ones with the best bot filters. They’ll be the ones that stopped mistaking activity for intent.

Source: Digiday