What Is an Attribution Window?
An attribution window is the defined time period during which a conversion can be credited to a specific marketing touchpoint. If a user clicks a paid search ad on Monday and purchases on Friday, a 7-day click attribution window captures that sale as a conversion tied to the ad. A 1-day window does not. The window you choose directly determines which campaigns appear to be working and which do not.
Attribution windows are a foundational setting in every major ad platform, including Meta Ads, Google Ads, and TikTok Ads. Misreading or mismatching these settings is one of the most common sources of inflated or deflated return on ad spend figures across marketing teams.
Click-Through vs. View-Through Windows
Platforms typically offer two distinct window types that measure different user behaviors.
- Click-through attribution window (CTA): Credits a conversion to an ad that a user clicked within the window period. A 7-day click window means the platform credits any purchase made within 7 days of a click to that ad.
- View-through attribution window (VTA): Credits a conversion to an ad that a user saw but did not click. A 1-day view window means if someone sees a display or video ad and converts within 24 hours through any other channel, the original impression still gets partial or full credit.
View-through windows are especially common in awareness-stage campaigns and programmatic display. They tend to produce higher reported conversion counts because they capture passive exposure, which makes view-through conversions a contested metric among performance marketers.
Common Attribution Window Lengths
| Window Length | Common Use Case | Platform Default |
|---|---|---|
| 1-day click | Impulse purchases, lead gen with fast follow-up | Meta (optional) |
| 7-day click | Standard e-commerce, subscription sign-ups | Meta (default as of 2021) |
| 7-day click + 1-day view | Balanced e-commerce with brand awareness layer | Meta (optional) |
| 28-day click | B2B, high-consideration purchases | Deprecated by Meta in 2021 |
| 30-day click | Long sales cycles, enterprise SaaS | Google Ads (optional) |
| 90-day click | Enterprise deals, luxury goods | Google Ads (optional) |
Meta Ads reduced its default attribution window from 28-day click to 7-day click in January 2021, partly in response to Apple’s iOS 14 privacy changes. Advertisers who did not adjust their historical benchmarks reportedly saw performance drops of 20 to 40 percent in reported conversions, even when underlying sales remained stable.
How Attribution Windows Affect Reported ROAS
The same campaign can produce dramatically different reported return on ad spend figures depending on the window applied. Consider a direct-to-consumer apparel brand running a retargeting campaign:
- Ad spend: $10,000
- Revenue attributed under 1-day click window: $18,000 (ROAS: 1.8x)
- Revenue attributed under 7-day click window: $34,000 (ROAS: 3.4x)
- Revenue attributed under 7-day click + 1-day view: $51,000 (ROAS: 5.1x)
None of these figures is necessarily fraudulent. Each simply answers a different question. The 1-day click window asks: “Who bought immediately after clicking?” The 7-day view window asks: “Who was exposed to the ad and bought at any point in the week, through any channel?” The latter captures customers who may have converted via organic search or direct traffic after the ad exposure, making the channel look more effective than it was in isolation.
Attribution Windows and the Attribution Model
The attribution window defines when credit is assigned. The attribution model defines how credit is distributed across multiple touchpoints within that window. A 7-day window under a last-click model gives 100 percent of the credit to the final touchpoint before conversion. A 7-day window under a linear model splits credit equally across every touchpoint in the week. Changing either variable changes the reported contribution of any given channel.
This interaction means that comparing two campaigns using different window-and-model combinations produces data that cannot be directly compared. Consistent window settings across all campaigns in a given account is a prerequisite for meaningful cross-campaign analysis.
Platform Differences to Know
Each platform manages attribution windows according to its own defaults and limitations.
Meta Ads
Meta’s Ads Manager defaults to a 7-day click, 1-day view window. Advertisers can adjust this in campaign settings or compare windows inside the Attribution Setting column. Since iOS 14, Meta’s Aggregated Event Measurement (AEM) limits the number of trackable conversion events per domain, which compresses reported window data further for some advertisers.
Google Ads
Google Ads allows windows from 1 day to 90 days for clicks and 1 to 30 days for engaged views. The default is 30 days for most conversion types. Google’s search-intent data means longer windows often capture genuine consideration cycles rather than coincidental exposure, making 30-day windows defensible for most categories.
TikTok Ads
TikTok defaults to a 7-day click, 1-day view window, similar to Meta. Given TikTok’s impulse-driven discovery format, some performance marketers argue that 1-day click windows more accurately reflect the platform’s actual contribution to purchases.
Choosing the Right Attribution Window
The most defensible starting point is to match the window length to the typical time between first ad exposure and purchase for the product or service being advertised. Three questions help calibrate this:
- What is the average consideration period? A $12 impulse buy on Instagram likely has a 1-day cycle. A $2,400 mattress may have a 14-day cycle. A B2B software contract may extend 60 to 90 days.
- What does first-party data show? Brands with CRM data or server-side tracking can measure the actual distribution of click-to-conversion lag times and set windows accordingly.
- How will this window affect optimization signals? Ad platforms use conversion data to train bidding algorithms. A window that captures very few conversions may starve the algorithm of signal, leading to poor automated bidding performance. Google’s Smart Bidding generally requires at least 30 to 50 conversions per month per campaign to optimize effectively.
Cross-Platform Attribution Window Conflicts
When multiple platforms run simultaneously, each claims credit for conversions within its own window. A customer who clicks a Facebook ad on Tuesday, a Google search ad on Thursday, and purchases on Friday will appear as a conversion in both Meta’s 7-day click report and Google’s 30-day click report. This last-click attribution double-counting is one reason platform-reported ROAS routinely exceeds blended ROAS calculated from actual revenue divided by total spend.
Media mix modeling (MMM) and incrementality testing are the primary methods for resolving these conflicts, as they measure contribution independently of platform-reported windows.
Frequently Asked Questions
What is the default attribution window on Meta Ads?
Meta Ads currently defaults to a 7-day click, 1-day view attribution window. This replaced the previous 28-day click default in January 2021, following Apple’s iOS 14 privacy changes. Advertisers can adjust the setting in campaign settings or use the Attribution Setting column to compare performance across multiple windows side by side.
What is the difference between a click-through and a view-through attribution window?
A click-through attribution window credits a conversion to an ad the user clicked within the window period. A view-through attribution window credits a conversion to an ad the user saw but did not click. View-through windows capture passive exposure and typically produce higher reported conversion counts, which is why view-through conversions are more contested as a performance metric.
Why does attribution window length affect ROAS?
A longer attribution window captures more conversions by crediting purchases that happen days or weeks after ad exposure. The same $10,000 campaign can report ROAS of 1.8x under a 1-day click window or 5.1x under a 7-day click plus 1-day view window, because each window answers a different question about when and how the user converted.
How do I choose the right attribution window for my campaigns?
Match the window length to your product’s typical consideration cycle. Impulse purchases under $50 generally fit a 1-day click window. Standard e-commerce works well with 7-day click. B2B software and high-consideration purchases often require 30 to 90 days. Brands with first-party CRM data can measure the actual distribution of click-to-conversion lag times to calibrate windows precisely. For more on how credit gets distributed once the window is set, see attribution models.
Key Takeaway
An attribution window is not a measure of truth. It is a measurement convention that determines what counts as a conversion for a given channel. Treating window-attributed ROAS as a direct proxy for channel value, without accounting for window length, view-through inflation, and cross-platform overlap, produces spending decisions based on reporting artifacts rather than real business outcomes. Standardizing windows, documenting them in campaign naming conventions, and cross-referencing platform data with first-party revenue data are the steps that close the gap between reported performance and actual performance.
For related reading, see conversion rate and view-through conversion.