Who can change the lookback window in GA4?

Someone with the Marketer role or above at the property level, according to Google's attribution settings help. Adding an annotation for the change takes the Analyst role or above, and reading annotations takes the Viewer role.

Does Google Ads follow GA4's lookback window?

Not by itself. Each Google Ads conversion action counts within its own conversion window, 30 days after a click unless you change it. If GA4 uses Paid and organic channels, Google says window changes for GA4 conversions must be made in GA4.

What does the Days to key event column measure?

How long a path took to reach its key event, in days. Google's report page describes the table as showing touchpoints, revenue and the time taken for a key event. A path cannot reach further back than your lookback window, so neither can this column.

GA4 lookback window: how to check and set it, step by step

Open Admin, Data display, Events, Attribution settings and read both lookback windows. Check Days to key event in Attribution paths and pick the window your slow buyers need. Save it, annotate the date and match Google Ads' conversion window.

By Joris van Huët, Founder & CEOUpdated 2026-10-018 min read

Run the numbers for your store: the free attribution window calculator.

Open Admin, then Events under Data display, then Attribution settings, and read the key event lookback windows. Purchases usually sit at 90 days. Before you change anything, check how long your buyers take in the Attribution paths report. Then save, annotate the date and line up Google Ads, because the change only counts from that day.

Eight steps, one GA4 property and one Google Ads account. Changing the window takes the Marketer role or above on the property, and an annotation takes Analyst or above. Google's help pages name two of the buttons in two ways, so both names appear below.

Step by step

Open the attribution settings. Google's settings page says: in Admin, under Data display, click Events, then Attribution settings. Its newer page on the reporting model calls the same button Key events attribution. Menu path: GA4 > Admin > Data display > Events > Attribution settings (or Key events attribution).
Read the purchase window. Purchases count as other key events: the default is 90 days, with 30 or 60 days as the alternatives. Write down what yours says before you touch it. Menu path: Attribution settings > Key event lookback window.
Read the acquisition window as well. Google counts first_visit and first_open as acquisition key events. Their window defaults to 30 days, with 7 days as the alternative. Engaged-view key events have a default setting of 3 days. Menu path: Attribution settings > Key event lookback window, acquisition key events.
Measure how long your buyers take. The paths report selects every key event by default and adds them together, so untick all but purchase. Then sort the table by Days to key event, slowest first. Menu path: GA4 > Advertising > Attribution > Attribution paths; Google's report page calls it Key event attribution paths, under the Key events drop-down.
Check which dates get the credit. The attribution models report defaults to Event time. That credits touchpoints in the lookback window before the key events in your date range. Ad interaction time credits the touchpoints that happened inside the range. Menu path: GA4 > Advertising > Attribution > Attribution models > Customize report > Reporting time.
Pick the window and save. If slow paths that carry real revenue run close to your window, choose the longest option. If they all finish early, a shorter window changes little. Google says the change applies going forward and shows in all reports. Menu path: Attribution settings > Key event lookback window > Save.
Annotate the day you changed it. Right-click that day's data point on any line graph and choose Add annotation. The title takes up to 60 characters, and the note then shows on every report with a line graph. Menu path: GA4 > Reports > right-click a data point > Add annotation. The full list sits in Admin > Data display > Annotations.
Line up Google Ads. Each Google Ads conversion action records conversions within its own window, 30 days after a click unless you change it. If GA4's attribution settings use Paid and organic channels, Google says window changes for GA4 conversions must be made in GA4. Menu path: Google Ads > Goals > Conversions > Summary > (conversion action) > Edit settings > Click-through conversion window.

A worked example

For illustration, follow one invented buyer through two settings. Say the buyer clicks a Meta ad on 1 March and an email on 2 April. In this worked example, they buy on 14 April after clicking a Google Ads search ad.

With a 90-day window, all three touches sit inside it in this worked example. The path reads Paid Social, Email, Paid Search, and a data-driven model can give the Meta click a share.

Now, for illustration, shorten the window to 30 days. Counted the way Google's January example counts, the edge falls on 16 March for a purchase on 14 April, in this worked example. The Meta click falls outside, so the path shrinks to Email, Paid Search. Last click hands Paid Search the sale either way. Any credit the Meta click had moves to the two later touches.

The other platforms keep their own clocks. Meta's standard settings count purchases at most 7 days after a link click. In this worked example the Meta click is 44 days old, so Meta never counts the sale. In this worked example, Google Ads counts its own 14 April click under any click-through window it offers, from 1 to 90 days. One sale, three verdicts, and none of them is a bug.

Nothing changes for sales before the switch, because the new window only applies going forward. So any date range that spans the switch mixes two rules. That is what the annotation in step 7 is for.

How often does a journey run that long? One store's export gives a feel for it. Journeys of 4 to 9 touches took 16.9 days to buy, and journeys of 10 or more took 16.0 days (Journeys sheet). Both fit inside even the shortest purchase window, but each figure covers many paths, so a slow tail can still hide inside.

Most of that store's revenue never meets the question. Journeys with 1 touch hold 79.5% of revenue and took 0.5 days (Journeys sheet), so every window gives them the same answer.

What should I check when the report looks wrong?

There is no Attribution settings button. Google's newer help page calls it Key events attribution, in the same place under Events. Without the Marketer role or above, you can look but not change it.
Old reports did not move after you saved. That is the design. Google applies lookback changes going forward; only a new reporting model rewrites past data.
A month's report credits clicks from the month before. Reporting time is on Event time, the default. Switch it to Ad interaction time to keep the credit inside your dates.
Early channels lost credit after a shorter window. Their touches now sit outside it, so every GA4 report leaves them out. That is the fence moving, not the channel getting worse.
Google Ads and GA4 disagree on a purchase. Each Google Ads action keeps its own conversion window. Line it up in step 8, or note the gap.
First-visit credit looks thin after a change. Acquisition key events only credit touches inside their own window, so a 7-day setting drops anything older. Check it in step 3.
Path exploration shows less history than the reports. Explorations follow your data retention setting, and standard reports do not.

What to do this week

Settle the purchase window on evidence. Sort last quarter's purchase paths by Days to key event, then save the window that covers your slow buyers. Pass: you can say why the window is what it is. Fail: it is whatever it was when you found it.
Match Google Ads to it. Open your purchase action's Click-through conversion window under Edit settings. Pass: it matches GA4's window, or you can say why it does not. Fail: the two differ and nobody chose that.
Read last month in Ad interaction time. In Attribution models, set Reporting time to Ad interaction time and pick last month. Pass: you see what each channel earned from that month's touches. Fail: you compare one month of spend with credit for older clicks.

Check the homework. Your GA4 Attribution paths export already holds the evidence. Causality Engine reads that one file and shows what each channel caused next to what last-click gave it, in 1 to 2 minutes, for €99 once (excluding VAT), refundable within 30 days. Check the homework

Frequently asked questions

Who can change the lookback window in GA4?
Someone with the Marketer role or above at the property level, according to Google's attribution settings help. Adding an annotation for the change takes the Analyst role or above, and reading annotations takes the Viewer role.
Does Google Ads follow GA4's lookback window?
Not by itself. Each Google Ads conversion action counts within its own conversion window, 30 days after a click unless you change it. If GA4 uses Paid and organic channels, Google says window changes for GA4 conversions must be made in GA4.
What does the Days to key event column measure?
How long a path took to reach its key event, in days. Google's report page describes the table as showing touchpoints, revenue and the time taken for a key event. A path cannot reach further back than your lookback window, so neither can this column.

Go deeper: Causal attribution, explained.

Sixty-second versions of these ideas: Causality Engine on YouTube Shorts.

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