GLOBEWICK
Attribution Windows Explained: Why Your Ad Platform and Analytics Disagree
Meta Ads, Google Ads and GA4 report different numbers for the same sales because they use different attribution windows, different attribution models and different data. Meta credits a sale to an ad someone clicked in the last 7 days or viewed in the last day. GA4 by default spreads credit across the touchpoints it can see, using its own lookback window. Each platform also counts conversions that the others cannot see. None of them is lying. They are answering different questions.
What an attribution window is
An attribution window is how long after someone interacts with an ad a platform will still give that ad credit for a conversion. There are two kinds:
- Click-through window: the time after someone clicks an ad. Meta's default is 7 days.
- View-through window: the time after someone sees an ad without clicking. Meta's default is 1 day.
So if someone sees your Instagram ad on Monday, does not click, and buys from a Google search on Monday evening, Meta can count that sale under 1-day view. Google Ads can count it too, because the person clicked a search ad. The sale appears twice across platforms but only once in Shopify.
Default windows by platform
| Platform | Default setting | What it can see |
|---|---|---|
| Meta Ads | 7-day click, 1-day view | Its own ads, including people who saw but did not click |
| Google Ads | Usually 30-day click for website conversions, data-driven model | Google ads only (Search, Shopping, YouTube, Display) |
| GA4 | Data-driven model, 90-day lookback for most conversions | Website sessions from all channels, but not ad views |
| Shopify | Last non-direct click, based on UTM and referrer | Actual orders, with limited channel detail |
Defaults change from time to time, so check your own settings: in Meta Ads Manager under the ad set's attribution setting, in Google Ads under Goals, and in GA4 under Admin, then Attribution settings.
Why the numbers never match
- Different windows. A sale 20 days after a click counts in Google Ads but not in Meta's 7-day window.
- View-through conversions. Meta counts people who only saw an ad. GA4 never sees ad views, so it gives that sale to whatever channel brought the final visit.
- Different models. Each ad platform tends to give itself full credit. GA4 shares credit across channels.
- Tracking gaps. Ad blockers, iOS privacy limits and cookie consent stop some browser events. Meta fills gaps with modelled conversions. GA4 uses its own modelling.
- Time zones and dates. Meta reports the conversion on the date of the ad interaction. GA4 and Shopify report it on the date of the purchase.
Which number should you trust?
Use each for what it is good at:
- Your store or CRM is the truth for total orders and revenue.
- Ad platforms are best for comparing campaigns, ad sets and creatives inside that platform, because the comparison is consistent.
- GA4 is best for comparing channels against each other with one consistent method.
For budget decisions across the whole business, watch blended numbers: total revenue ÷ total ad spend (often called MER), and new customers ÷ total spend (blended CAC). If blended results improve when you raise Meta spend, Meta is working, whatever the attribution report says. We explain how to calculate this properly in how to calculate your real customer acquisition cost.
How to reduce the gap
- Set up server-side tracking. Meta's Conversions API and Google's enhanced conversions recover events that browsers block. On Shopify, the native Meta and Google channel apps can handle this.
- Use consistent UTM tags on every ad so GA4 and Shopify can see which campaign a visit came from.
- Compare like with like. When checking Meta against GA4, use Meta's "7-day click" column only and exclude view-through.
- Deduplicate in reporting. Do not add Meta-reported sales and Google-reported sales together. The sum will usually be higher than your actual orders.
- Run incrementality tests for big decisions. Pause a channel in one region or run a Meta conversion lift study to see how many sales actually disappear.
Should you change Meta's attribution window?
For most e-commerce brands, 7-day click and 1-day view is the right default, because it gives the algorithm the most signal. Switch to 7-day click only if view-through conversions are inflating results, for example when retargeting people who were going to buy anyway. Lead generation advertisers with long sales cycles often still keep 7-day click, because the platform optimises on the lead, not the eventual sale.
FAQ
Why does Meta show more purchases than Shopify?
Usually because of view-through conversions and because Google or another channel also touched the same sale. Meta counts a sale its ad influenced, even when another channel got the final click.
Why does GA4 show fewer conversions from Facebook than Meta Ads Manager?
GA4 cannot see ad impressions, so it never credits view-through sales, and it shares credit with other channels in the path.
What attribution window should B2B advertisers use?
Optimise ads on the lead with 7-day click, then measure revenue in your CRM using offline conversion imports, which carry the sale back to the original campaign.
Not sure your tracking is set up correctly? Our Google Ads and Meta Ads audits start with tracking, because every decision depends on it.