TL;DR
GA4 replaced its preset lookback windows with custom integer values on August 11, 2026 [1]. Click-through conversions (CTC) previously offered 1, 7, 14, 30, 60 or 90 days and now take any integer from 1 to 90. Engaged-view conversions (EVC) were fixed at 3 days and now take any integer from 1 to 30 [1]. Google says the update lets Google Analytics "align conversion attribution lookback windows more closely to your unique business cycles" [1]. For a Shopify store that means one decision worth making deliberately: how many days pass between the ad interaction and the order, for your catalog, not for a preset. A store selling a $19 phone case and a store selling a $2,400 mattress have different purchase cycles, and the setting now stretches to fit both. GA4 also carries a separate lookback control, the key event lookback window under Admin > Data display > Events, and that is the one Google's documentation ties to session attribution [3][4].
Key Takeaways
- Both conversion windows now take custom integers: CTC 1 to 90 days, EVC 1 to 30 days. EVC was previously fixed at 3 days, CTC was previously a list of six presets [1].
- The path is
Advertising > Conversion management, then the more options menu and Settings. Properties linked to Google Ads can also reach the equivalent controls from Google Ads conversion management [1]. - Google's stated purpose is aligning windows to your business cycle [1]. That is an instruction to measure your own time to purchase.
- A different control, the key event lookback window at
Admin > Data display > Events > Attribution settings, still uses presets, and Google says the value you choose there also applies to session attribution [3][4]. That is the setting that moves GA4 acquisition reporting. - Google's documentation of the August 11 release does not state whether the CTC and EVC change is retroactive, in either direction. Plan the change as though reports before and after the switch are on different settings, and note the date you flipped it.
- Per-conversion attribution settings arrived earlier, in a January 16, 2026 release that Google labeled Beta and said "may not be available" to every property [2]. Check what your property actually shows before planning around it.
- On Shopify, the window only helps if the purchase reaches GA4 with its identity intact. A server-side purchase that arrives without a click ID has nothing to match against, whatever the window is set to.
What changed on August 11, 2026?
Two numbers stopped being a menu.
Click-through conversion windows used to be chosen from six values: 1, 7, 14, 30, 60 and 90 days. They now accept any integer between 1 and 90. Engaged-view conversion windows were not a choice at all. They were fixed at 3 days, and the release opened them to any integer between 1 and 30 [1].
| Window | Before August 11, 2026 | After |
|---|---|---|
| Click-through (CTC) | Presets: 1, 7, 14, 30, 60, 90 days | Any integer, 1 to 90 days [1] |
| Engaged-view (EVC) | Fixed at 3 days | Any integer, 1 to 30 days [1] |
The EVC half is the bigger change even though it carries the smaller number. Before August 11 there was no EVC window to choose at all: every property ran on 3 days [1]. Now it is yours to set, up to 30.
Google's own framing for the release is short: the update lets Google Analytics "align conversion attribution lookback windows more closely to your unique business cycles" [1].
One question the release note leaves open: whether adjusting a CTC or EVC window reprocesses historical data or only applies going forward. Google's August 11 documentation does not say, in either direction. Anyone telling you it is retroactive, or that it definitely is not, is filling a gap in the documentation with confidence. Record the date and the old value before you save, so that a later comparison has a reference point regardless of which way it works.
Where the setting lives
Open Advertising > Conversion management in your GA4 property. Find the conversion you want to change, open the more options menu and choose Settings. If the property is linked to Google Ads, the same controls are reachable from Google Ads conversion management for the linked conversions [1].
Two things to check before you go looking for a control that is not there. First, per-conversion attribution settings themselves shipped as a Beta on January 16, 2026, and Google's note on that release said the feature "may not be available" [2]. Second, Google's documentation of the August 11 change does not state that every property has it. So treat a missing control as a rollout state and check again in a few days rather than filing a support ticket the same afternoon.
Which window matches your purchase cycle?
The honest starting point is your own order data, and Shopify has it. Pull a few hundred recent orders and look at the gap between the customer's first session and the order. Measure it in days, and take the median. That number is the one Google is asking you for.
Run the arithmetic on an illustrative store selling a $180 winter coat. Say the typical buyer sees a video ad, does nothing for a week, comes back through a branded search, and orders on day 12. Under the old fixed 3-day EVC window, day 12 falls outside the window. Set EVC to 14 and day 12 falls inside it. The arithmetic is the whole change.
Rough starting positions, to be replaced by your own numbers within a month:
| Store type | Typical shape | Starting CTC | Starting EVC |
|---|---|---|---|
| Impulse goods under $30 | Same-session or next-day purchase | 7 days | 3 to 7 days |
| Considered purchase, $100 to $500 | Multiple sessions across one to two weeks | 30 days | 14 days |
| High-ticket or furniture | Research over weeks, offline consultation | 60 to 90 days | 30 days |
| Subscription first order | Short decision, long value tail | 14 days | 7 days |
Keep the window a little longer than your real cycle. A 90-day CTC window on a store whose buyers decide in two days mostly credits clicks that had nothing to do with the order, and you will see it as inflated performance on your least targeted campaigns.
The key event lookback window is a separate control
GA4 has a second lookback setting, and it lives somewhere else entirely: Admin > Data display > Events > Attribution settings [4]. It is the key event lookback window, and it still works on presets rather than custom integers: 30, 60 or 90 days for most key events, with 90 as the default, and 7 or 30 days for first_open and first_visit, with 30 as the default [4].
This is the control Google's documentation ties to session attribution. The note reads: the key event lookback window you choose also applies to session attribution [3][4]. So changing this window changes which sessions GA4 hands credit to across acquisition reporting, not only what ad platforms are credited with. Google also documents its timing behavior here: changes to attribution settings "apply going forward and are reflected in all reports" [4].
What Google's documentation does not say is whether the new custom CTC and EVC conversion windows interact with this key event lookback window at all. The August 11 release note covers the Advertising-side windows, the attribution settings page covers the key event window, and neither one references the other. Treat them as two settings until Google says otherwise, and change one at a time so you can tell which produced which movement.
If you are the person who explains a sudden channel shift to a marketing team every Monday, the day you touch the key event window is a day worth writing on the calendar. Our piece on GA4 attribution models on Shopify covers the model selection that sits next to these settings, which is a separate control again and does a different job.
How should a Shopify store roll this out?
Change one conversion at a time, starting with purchase. Note the date. Give the new window at least one full purchase cycle before you judge the numbers, and remember that reporting delays sit on top of the window: a fresh Google Ads conversion action has its own multi-hour warm-up before anything appears, which is a different problem with an identical symptom.
Then check the input side, because a lookback window can only credit a conversion that arrived with something to match against. On a Shopify store the purchase event fires server-side from the order webhook, which is what makes it survive ad blockers and closed browsers. WeltPixel Conversion Tracking sends that purchase within seconds of the order, carrying the click identifiers captured earlier in the visit, including gclid, gbraid and wbraid for Google Ads. That bridge depends on the theme app embed being enabled. With it enabled, the events and the click identifiers travel together, which is the condition a lookback window needs before it can credit anything at all. Without it, you get the pattern people blame on attribution windows: conversions present, credit missing. The related settings on the Google Ads side are covered in our piece on server-side enhanced conversions.
Last, leave at least a week between changing a window and changing the attribution model. Two moving settings produce a chart nobody can explain, and one of them will get blamed for the other's effect. Broader context on how windows and delays interact on Shopify is in our attribution windows and reporting delays guide.
FAQ
What is the maximum GA4 conversion lookback window now?
90 days for click-through conversions and 30 days for engaged-view conversions, and both accept any whole number of days in that range as of the August 11, 2026 release [1].
Was the engaged-view window really fixed at 3 days before?
Yes. Google's release note describes the previous EVC behavior as a fixed 3-day window, replaced by a custom range of 1 to 30 days [1].
Does changing the lookback window rewrite my historical reports?
For the CTC and EVC conversion windows, Google's documentation of the August 11 release does not state whether the change applies retroactively. Because the answer is not documented, treat the switch date as a boundary in your reporting and label it, rather than assuming either behavior. For the separate key event lookback window, Google documents that attribution setting changes "apply going forward and are reflected in all reports" [4].
Does the lookback window affect anything outside Google Ads reporting?
That depends on which window. The CTC and EVC windows are Advertising-side settings. The key event lookback window, set at Admin > Data display > Events > Attribution settings, is the one Google says also applies to session attribution [3][4], so changing that shifts GA4's own acquisition reporting. Google's documentation does not say whether the new CTC and EVC windows interact with the key event window.
Where do I find the setting?
Advertising > Conversion management, then the more options menu and Settings. Linked properties can also manage the equivalent settings from Google Ads conversion management [1]. The key event lookback window is elsewhere, at Admin > Data display > Events > Attribution settings [4].
If your purchase events are already arriving server-side with their click identifiers attached, the window is the only variable left to tune. WeltPixel Conversion Tracking handles that delivery for GA4, Meta, TikTok, Google Ads, Reddit, OpenAI Ads, Pinterest Ads, Snapchat and Klaviyo from one Shopify app: install it here.
Sources
- Google Analytics Help, [GA4] What's new in Analytics, August 11, 2026 entry, support.google.com/analytics/answer/9164320, accessed August 24, 2026
- Google Analytics Help, [GA4] What's new in Analytics, January 16, 2026 entry, support.google.com/analytics/answer/9164320, accessed August 24, 2026
- Google Analytics Help, [GA4] Identify and exclude unwanted referrals, support.google.com/analytics/answer/10327750, accessed August 24, 2026
- Google Analytics Help, [GA4] Select attribution settings, support.google.com/analytics/answer/10597962, accessed August 24, 2026