Attribution
First-click attribution
Also called first touch.
First-click attribution is a model that gives all credit to the first campaign touch inside the lookback window. It answers 'what started this'.
How it is measured
For each conversion, the model walks back through the touches in the window and picks the earliest one. All value goes to its channel and campaign. Later touches get nothing.
Choose the lookback with care. A 90-day window finds more first touches than a 7-day one, and a cookieless tool only sees the touches inside what it can link, so check what history the tool can actually connect.
Worked example
A stand-up desk maker sees 585 orders in a quarter. First-click credits podcast ads with 212 of them, even though the podcast link was tagged only for people who typed a vanity address.
Last-click credit for the same orders gives podcast ads only 31, because most buyers return through search just before buying. The maker keeps the podcast through the next quarter, since it opens the funnel that search closes.
How it differs
First-click attribution rewards the opener. Last-click attribution rewards the closer. Neither credits the middle of a long path.
Common errors
Using it to judge closing channels. Setting a very short lookback. Overlooking untagged first touches. Treating it as proof that the first channel caused the sale. Comparing it with last-click without stating windows.
In practice
Use it to find which channels bring new people in. Pair it with a last-click view to see who closes. Do not move whole budgets on one model.