What is First-Click Attribution?

First-click attribution (first-touch, first interaction) assigns 100% of conversion credit to the first ad click on the path. Intermediate and closing clicks get no share. It is the third single-touch model next to last-click and the multi-touch family: credit is not split and does not go to the final click.

Example. A user clicks a push ad on Monday (source A), three days later clicks a Meta retargeting ad (source B), and completes an order. First-click credits A. Last-click credits B. View-through impressions are usually outside classic first-click (that is a separate view-through rule).

Attribution answers “who gets the action.” First-click asks a different question than last-click: who brought the person into the funnel, not who closed the sale. It still uses click IDs, cookies or device IDs and an attribution window — only the selection rule changes.

How it is implemented

The system stores the first click identifier and does not overwrite it on later visits inside the window. Trackers keep a first click ID beside the last click ID. In web analytics, first-click was a Universal Analytics comparison model (First Interaction). GA4 uses a different set (data-driven by default, plus last-click variants), but first-touch still appears in CRM and internal reports: first-visit channel vs conversion channel.

On paper the rule is simpler than last-click. In practice you must persist the first click and stop retargeting from replacing it. If the cookie lasts 7 days and the sales cycle is 30, first-click breaks the same way last-click does — in the opposite direction.

First-click vs last-click

Last-click is the de facto payout standard in CPA networks: one postback, one clickid, one source per conversion. First-click almost never sets the partner payout. It is used so top-of-funnel work is not written off.

Last-click credits retargeting, brand search, and email — channels near the end of the path.
First-click credits prospecting: push, in-app, cold native, a first video click.
Both are single-touch: 100% to one touch. Neither is “more truthful”; they are different slices of the same path.

Gaps between the ad account, the tracker, and the network often reflect model mismatch (assisted / data-driven / first-click comparison vs last-click payout), not “lost” conversions. Reconciliation without naming the model is meaningless.

Vs multi-touch

Multi-touch splits value across touches (linear, time-decay, U-shaped, data-driven). First-click is not MTA: mid-path touches get zero. U-shaped is a closer compromise (weight on first and last) but a different model. In arbitrage, MTA rarely moves money; first-click is even more an analytic lens, not a billing rule.

Where the model is useful

Long cycles (finance, insurance, B2B lead): the first paid click is often informational; close happens on brand or retargeting. Last-click-only optimization makes prospecting look expensive even though retargeting has nothing to recapture without it.

Mobile apps: first click or impression before install vs later re-engagement. MMPs and SKAdNetwork limit user-level paths; first-click at user grain is often unavailable, leaving an aggregated view.

Organic and direct: if the “first click” is SEO and a paid channel closes, first-click writes off performance. If the first click is paid and the conversion arrives as direct, last-click writes off the buy. Choosing a model is choosing the question, not finding a single truth.

Windows, cookies, and fraud

Without an explicit window (“first click within 7 / 30 / 90 days”) the model is undefined. ITP and ATT shorten first-touch cookies more than a short last-touch window. First-click is exposed to inflated first touches: cookie stuffing, interstitial clicks, first click-ID injection. Networks keep last-click partly because one last click is easier to dispute than “who was first a week ago.”

Practical minimum for a buyer: keep last-click as the source of truth for ROI and payouts; use first-click (or at least “first session source”) as a separate cut so prospecting is not killed on last-click EPC alone.