What is a Conversion window (aka Key Event Lookback Window) in GA4?

In the context of GA4, the ‘conversion window’ (Key event lookback window) is the time period (measured in days) that determines how far back in time a touchpoint (e.g., exposure to a marketing channel) is eligible for conversion credit.

For example,

A 30-day conversion window means a touchpoint is eligible for conversion credit for up to 30 days from the day it first occurred.

Similarly,

A 90-day conversion window means a touchpoint is eligible for conversion credit for up to 90 days from the day it first occurred.

Note: ‘Key events’ is a new name for ‘conversions’ in GA4. For more details, check out this article: GA4 Conversions vs Key Events.

Default Key event lookback window used by GA4

By default, GA4 uses the 30 days Key event lookback window for Acquisition key events (‘first_open’, ‘first_visit’) and 90 days Key event lookback window for all other key events for click-through key events:

GA4 uses a 3-day Key event lookback window for ‘Engaged-view key events‘.

You can not change this Key event lookback window setting.

The optimal setting for the GA4 Key event lookback window

Don’t follow Google’s recommendation for using 30 days conversion window for ‘Acquisition Key events’ and 90 days conversion window for all other key events in GA4.

Instead,

Set your conversion window to 7 days for Acquisition key events and 30 days for all other key events to get the most accurate reporting possible in GA4.

Using a longer conversion window because of longer sales cycles may produce optimum results in the world with no user consent, ad blockers, or privacy extensions.

But we don’t live in the year 2010 any more.

To get optimum results from conversion attribution in 2024 and beyond, using the narrowest possible attribution window is no longer optional but a mandatory requirement.

Otherwise, you will continue to get muddy analytical insight.

In the world of multi-channel marketing, a customer is exposed to multiple touchpoints over a long period of time.

Not all touchpoints are equally valuable.

For example, let’s say a user clicks on your LinkedIn post before purchasing on your website.

This act of reading and clicking on your LinkedIn post is far more valuable in influencing conversion than any ad click that occurred months ago because of the time decay factor and exposure to multiple touchpoints.

Now, GA4 can still give conversion credit to that Google ad your customer clicked on 80 days ago because of the default 90 days conversion window set for click-through conversions.

And if you are heavily involved in multi-channel marketing, using long conversion windows means many channels can take credit for the same conversion, which could result in overstated revenue.

The ‘overstated revenue’ metric can tell you whether your reported sales and ROAS figures are correct and whether you are as profitable as you think you are.

Overreporting occurs when one platform claims conversions from another. Or multiple platforms claim the same conversion because of long conversion windows.

So, for example, both Google and Facebook can claim that a particular order was generated via their platforms because of their 30 to 90-day conversion windows.

That’s why it is important to use the narrowest possible conversion windows for all your analytics and advertising platforms, regardless of the length of your sales cycle.

The use of a longer attribution window increases the likelihood of external factors influencing the conversion.

For example, if the conversion window is too wide, other marketing activities, customer touchpoints, or changes in market conditions may occur, making it difficult to attribute the conversion accurately.

By narrowing the conversion window, you can minimize the impact of such external factors and focus on the immediate impact of the tracked activity.

It does not matter which touchpoint or channel truly introduced your brand. What matters is the touchpoint/channel that most influenced conversions.

And time plays a great role in determining that influence.

For example, you are unlikely to make a purchase after clicking on an ad a year earlier. You are most likely to make a purchase after clicking on the ad within seven days.

Use the narrowest possible attribution windows for “all” your analytics and advertising platforms, not just for GA4.

FAQ: Why should I use a 7-day conversion window for acquisition key events when these events refer to the first customer touchpoint?

Isn’t the 7 days conversion window too short for knowing how your customers were introduced to your brand?

Here is the thing: When you use a longer window for traffic attribution, you will face the same issues as one faces when using a longer window for conversion attribution, i.e., many channels will claim that they introduced your brand to your customers.

The other technological limitation associated with the first touch model is that the lookback window cannot be longer than 30 days.

Therefore, if the first user interaction occurred more than 30 days ago, GA4 will not be able to record that interaction as the first interaction.

Often the true first touchpoints are never really recorded by any analytics tools or ad platforms. This makes the first interaction analysis kinda pointless.

The touchpoints which introduced your brand matter a lot less than the touchpoints which generated/influenced the desired conversions and which are closest in time to conversion.

But that does not mean I am advocating for the last-click attribution model.

It’s more like advocating for the time decay attribution model, which is by far the best model for conversion attribution. The DDA model is a black box. So can’t comment on that.

First influential touchpoints > First touchpoints.

In other words,

7 days acquisition key events > 30 days acquisition key events.

It does not matter which touchpoint or channel introduced your brand. What matters is the touchpoint/channel that has the most influence on conversions.

And time plays a great role in determining the influence.

For example, you are unlikely to make a purchase after clicking on an ad a year earlier. You are most likely to make a purchase after clicking on the ad within seven days.

Regardless of the length of your sales cycle, you can’t get wrong with the time decay model, which minimizes the impact of external factors like changes in marketing activities and market conditions on customers’ purchase journeys.

How to change the conversion window in GA4?

GA4 uses the conversion window (aka Key event lookback window) at the property level.

At present, it is not possible to set different lookback windows for individual reports within the GA4 property.

If you want to change the lookback window for Acquisition key events and/or other key events, then follow the steps below:

Step-1: Navigate to your GA4 property.

Step-2: Click on the ‘Admin’ link from the left-hand side navigation:

Step-3: Click on ‘Attribution Settings’ under ‘Data Display‘:

Step-4: Scroll down until you see the section named ‘Key event lookback window’. 

Step-5: Change the Key event lookback window for ‘Acquisition key events‘ to 7 days, ‘All other key events‘ to 30 days and then click on the ‘Save’ button:

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Important points about GA4 Key event lookback window

#1 Changing the Key event lookback window will only apply going forward, and these changes will be reflected in all reports within the GA4 property.

#2 Changing the Key event lookback window will affect all key events, including those imported to other products.

#3 The Key event lookback window applies to all GA4 attribution models and all key event types.

The Key event lookback window settings in GA4 significantly impact the key events imported to Google Ads.

Google Ads exclusively uses GA4’s Key event lookback window settings for imported key events, which means that this setting directly affects how key events are counted and reported in Google Ads.

Unifying Key event lookback windows ensures consistency in reporting between GA4 and Google Ads and provides reassurance in the accuracy of your data.

Google recommends reviewing and aligning your Key event lookback window settings in GA4 and Google Ads to ensure they match your campaign goals and objectives.