Attribution Windows Explained: How Lookback Settings Move Your Numbers
What click, engaged-view and view-through windows are, the verified Google Ads and GA4 defaults, Meta's March 2026 change, and how to log windows.
This page is part of Zenko's guide to marketing attribution discrepancies.
An attribution window, also called a lookback window, is how far back from a conversion a system will look for an interaction to credit. Change the window and the count changes, even though the same people did the same things.
The three kinds of window
- Click-through window. Looks back for an ad click.
- Engaged-view window. Looks back for a video engagement that qualifies under that platform’s rules. Meta's March 2026 announcement uses the related label "engage-through", described below.
- View-through window. Looks back for an ad impression that was seen but not clicked.
A longer window can make later conversions eligible for credit; it does not guarantee a higher count. View-through reporting considers eligible impressions rather than clicks. Neither mechanism establishes that an ad caused a purchase.
Verified defaults, read on 18 October 2026
| Platform | Window | Default | Adjustable | Source |
|---|---|---|---|---|
| Google Ads | Click-through | 30 days | 1 to 30, 60 or 90 days, for Search and Display campaigns, depending on conversion source | About conversion windows |
| Google Ads | Engaged-view | 3 days | 1 to 30 days | Same page (see note) |
| Google Ads | View-through | 1 day | 1 to 30 days or 1 to 4 weeks | Same page |
| GA4 | Acquisition key events (first_open, first_visit) | 30 days | 7-day option | Select attribution settings |
| GA4 | All other key events | 90 days | 30 or 60 days | Same page |
| Meta | Attribution window | Check your ad set setting | Not verified | See below |
Note on Google Ads: confirm each actual conversion-action setting in your account before comparing reports.
Meta: what we can and cannot say
On 3 March 2026 Meta announced that click-through attribution for website and in-store conversions would be limited to link clicks. Shares, saves and other non-link clicks move to a category renamed "engage-through", and the engaged video view threshold drops from 10 seconds to 5 seconds. Rollout was staggered from later in March 2026, and Meta said billing was unchanged. Meta's stated aim was to reduce measurement misalignment with tools such as Google Analytics (Simplifying Ad Measurement for a Social-First World).
We could not verify Meta's current default window. The Help Centre pages returned only their titles, and search summaries gave conflicting defaults. So this page states none. Open your own ad set, read the attribution setting, and record it with the date.
Which changes are retroactive
This is where windows cause the most confusion.
- GA4: changing the reporting attribution model affects both earlier and subsequent data in applicable event-scoped reports; user- and session-scoped traffic dimensions are unaffected, but lookback-window changes affect subsequent reporting rather than rewriting earlier data (Select attribution settings).
- Google Ads: a window change applies only to conversions from that day forward (About conversion windows).
If you shorten a window in March and compare April with February, the two periods were measured under different rules. Log the change date next to the numbers.
Why longer sales cycles make this matter
As a practical implication of the window definition, if a buying cycle is longer than the window, a later conversion may fall outside it and go uncredited, while a system with a longer window credits it. For teams with long cycles, the sensible response is to write down the cycle length you believe applies and see which windows could and could not reach it.
How to record windows in the ledger
In Table A of the Attribution Disagreement Ledger, fill these columns for every source:
- Attribution model
- Click, engaged-view and view windows
- Date settings last changed
Then, in Table B, name window difference as a cause only if the settings in Table A actually differ. For the Google pair specifically, see Google Ads vs GA4 conversions.
What this page does not do
It does not recommend a window length. The right window depends on your buying cycle and your decision, and your team should set it.