The attribution window (lookback window) is the length of time after an ad interaction during which a conversion can still be linked back to that interaction. If a user clicks an ad today and completes a purchase two weeks later, this window determines whether that purchase gets counted toward the ad.
The window length is a matter of interpretation — it doesn’t change the actual purchase behavior. A window that’s too short can miss real conversions; one that’s too long can attribute an unrelated conversion to the wrong ad. For example, if a user clicks an ad on day 1 and buys on day 25, a 30-day window would credit the conversion to the ad; had the same purchase happened on day 35, the window would already be closed and the conversion wouldn’t be attributed to any ad.
Google Ads’ conversion window documentation defines the window as “the amount of time after an ad interaction (such as a click or a video view) during which a conversion is recorded.” For the click-through window, the default is 30 days with a range of 1-90 days; for the view-through window, the default is 1 day with a range of 1-30 days.
The Click-Through Window
This window starts running from the moment a user clicks the ad. The default duration is 30 days, adjustable from 1 to 90 days depending on the source.
Window length matters in long sales cycles
In B2B or high-ticket purchases, the buying decision can take weeks. Consider an enterprise software service with an average sales cycle of 45 days: if you use the default 30-day window, some customers who first touched an ad but purchased after day 30 never show up in the report at all. In that case, the campaign might actually be working — the real problem isn’t the campaign, it’s the window setting.
A long window adds noise in short sales cycles
The reverse is also true. Using a 90-day window for a local service with a typical decision time of 2-3 days can attribute a purchase made months later, driven by an entirely different need, back to an old ad. This can make the campaign look more effective than it actually is.
The View-Through Window
This window applies to cases where a user only sees the ad without clicking it. The default duration is 1 day, adjustable up to a maximum of 1 to 30 days (in some cases 1-4 weeks).
View credit is treated more cautiously
A click is an active action by the user; a view is a passive exposure. That’s why the view-through window starts with a shorter default duration than the click-through window. For example, a user might notice a banner in a Display campaign while browsing without really registering it, then search for the brand directly and buy three days later — with the default 1-day window, this conversion wouldn’t be attributed to the ad, but with the window extended to 7 days, it could be. Setting both windows to the same length can obscure this difference and produce a misleading result.
The Engaged-View Window
There’s a separate window type for video campaigns. Its default duration is 3 days, adjustable up to a maximum of 1 to 30 days.
Video viewing behavior is evaluated separately
Watching a video for a certain duration represents a different level of engagement than simply seeing an ad. That’s why Google defines a separate window type for video; conflating it with the other two windows can lead to misreading the report.
How Should You Choose a Window Length?
The right duration depends on the product’s purchase cycle — there’s no single correct answer.
| Example category | Typical decision time | A window roughly matching it |
|---|---|---|
| Fast food, small consumer goods | Minutes to hours | 1-7 days |
| Apparel, mid-priced e-commerce | A few days | 7-14 days |
| Home goods, mid-to-high-priced products | 1-3 weeks | 14-30 days |
| B2B software, enterprise services | 3-8 weeks | 30-90 days |
This table isn’t a hard rule, just a starting point. The actual sales cycle should be measured from CRM data or historical sales records, and the window calibrated accordingly.
A minimum duration is recommended for sufficient data
Google Ads documentation states that windows of at least 7 days provide richer conversion data. There’s no documented clear-cut maximum broken down by channel (Search, Display, YouTube), so the general range above should be treated as guidance. The window length also affects how much historical data data-driven attribution can work with — that relationship is covered further in What Is Data-Driven Attribution?.
Pre-Launch Checklist
When reviewing your window setting:
- Does the current window length match the product’s actual purchase cycle?
- Have click-through and view-through windows been evaluated separately?
- Is the reporting difference after a window change being confused with an actual performance change?
A Common Mistake
The most common mistake is applying the same default window to every campaign without ever considering the product or service’s real decision time. In a service with a long decision cycle, a short window can leave a significant share of real conversions out of the report.
The second mistake is concluding “conversions went up” right after changing the window length. Extending the window brings in conversions that already happened in the past but weren’t counted under the previous, shorter window — that’s an expansion of the measurement window, not a performance increase.
Summary
The attribution window is the length of time after an ad interaction during which a conversion can still be counted. The click-through window defaults to 30 days, view-through to 1 day, and engaged-view to 3 days. The right duration should be set based on the product’s actual purchase cycle, and the reporting difference caused by a window change shouldn’t be confused with an actual performance change.