GEO & AI search

Referrer stripping

Definition

When a visit arrives without the HTTP Referer header that names the page the shopper came from, because the source page, the link or the app withheld it. Analytics tools then classify the visit as Direct. It is the main reason AI traffic is undercounted.

Defined in AI Traffic and Attribution: How to Measure What ChatGPT, Gemini and AI Mode Send Your Store.

Related terms

AI-attributed revenue: Purchase revenue from sessions whose source GA4 can identify as an AI assistant, using last-click attribution within the session. It excludes purchases influenced by AI answers that arrived through Organic Search, Direct or another channel, so it understates AI's total effect.
AI Assistant channel: A channel in GA4's default channel group for visits from AI assistants such as ChatGPT, Gemini, Deepseek, Copilot and Grok. Its rule is that the medium exactly matches ai-assistant. GA4 sets that medium, and the campaign (ai-assistant), when the referrer matches Google's list of AI assistants. Google says the channel excludes its own AI Overviews and AI Mode.
Custom channel group: A copy of GA4's default channel group that you can edit: add channels, change conditions and reorder them. Traffic goes to the first channel whose definition it matches. Standard properties can have two custom groups, 360 properties five, each with up to 50 channels. Google says custom groups can be applied to reports retroactively.
OpenAI Measurement Pixel: OpenAI's browser SDK for ChatGPT Ads. You install a script, initialize it with a Pixel ID created in the Conversions section of Ads Manager, and call oaiq("measure", ...) when a conversion happens, such as order_created for a purchase.
Conversions API: OpenAI's server-to-server endpoint for ChatGPT Ads conversion events. Your backend posts confirmed events, such as a paid order, with a Pixel ID and a separate Conversions API key. OpenAI calls it a more reliable tracking source than the Pixel alone.
oppref: The OpenAI click reference appended to the end of a ChatGPT ad's landing page URL (for example ?oppref=gAAAAAb123). The Pixel captures it and stores it in a first-party __oppref cookie for 30 days; server events should pass the original value unchanged.

All 157 terms

What is AI invisibility costing you?

Revenue at risk from AI shopping channels, with the formula shown so you can check the maths.

Open the calculator Commerce GEO