What Is an Attribution Window?

How Does an Attribution Window Work?

An attribution window is a time limit on credit: when a conversion is recorded, the platform looks back over the window you set and credits its ad only if the click or view happened inside it. LinkedIn's help page, for example, calls the conversion window "also known as a lookback window" and describes it as "the timeframe for when conversions are attributed to a LinkedIn ad."¹

Every platform in the table below has separate rules for clicks and for views (an ad someone was shown but didn't click, which What Is a View-Through Conversion? covers), and in Google Ads both are set on each conversion action, so with a 7-day click window "any conversion that happens more than 7 days after the ad interaction won't be recorded."²

The window decides whether a platform gets credit, while the attribution model decides how that credit is split among several ads, and Which Attribution Model Should You Use? covers the second half. Both are settings inside the platform, which is why the Channel Selection step treats every platform report as a second opinion beside a source of truth you control.

What Are the Default Attribution Windows on Each Platform?

The defaults differ by platform and by type of interaction, and some aren't stated at all, so the only reliable answer for your account is the setting on each conversion, though each platform's documentation gives the starting point.

Attribution windows as each platform's documentation describes them

The table holds two surprises, the first being that LinkedIn's default view window runs to 90 days¹ while Google's and Microsoft's view windows default to 1 day,²⁵ so a LinkedIn report and a Google report can be counting different things under the same word "conversions". The second is that Google Analytics 4 has its own lookback window, set in its own attribution settings,⁶ so check it separately before comparing GA4 with Google Ads.

How Does the Attribution Window Change Reported Results?

A longer window credits more conversions to the ads and a shorter one credits fewer, even though the same buyers signed either way. Microsoft's documentation warns that "a shorter conversion window will reduce the number of conversions your account records,"⁴ which moves the numbers people quote in three ways:

• Cost per conversion and return on ad spend move with the window, because the spend stays the same while the conversion count rises or falls, so a channel can look better or worse after a settings change with nothing different in the market.
• Channels with different windows can't be compared fairly, since a platform crediting views for weeks will claim more of the same buyers than one crediting views for a day, and when two platforms both count a buyer, the totals add up to more customers than you signed.
• Period-to-period comparisons break when someone changes a window, because LinkedIn, Microsoft and GA4 all apply a change only from that point on,¹⁴⁶ so last quarter's figures were counted under the old rule.

A longer window isn't wrong in itself, because one shorter than the time your buyers take to act leaves real conversions uncredited, while one much longer credits ads with sales they had little to do with.

Why Doesn't Any Default Window Match a B2B Sales Cycle?

A platform's window counts whatever conversion you told it to count, which in the lead-generation accounts we review is usually a form fill or a call, while a B2B sale can sign months after that first click, in a meeting the ad platform never sees. Even LinkedIn's longest options, 180 or 365 days, are offered only for some conversion types sent through its Conversions API or a CSV upload.¹

Sending signed deals back to the platforms has limits too, since Google keeps the click ID it needs to match an offline sale for 90 days, so a sale that signs later has to be sent as an earlier stage that happens within 90 days of the click.⁷ What Is Offline Conversion Tracking? covers how that upload works and which stages to send.

So the platforms are good at telling you which ads produced leads within their windows, and poorly placed to tell you which ads produced customers. Take a commercial HVAC contractor with about forty million dollars in annual revenue, which sells maintenance agreements to property management firms through Google search, LinkedIn ads aimed at property and facilities managers, and a local building owners' association.

The full quarter, with each platform's claims set against the agreements signed, is on How Do You Measure Digital Marketing ROI?.

How Do You Choose the Right Attribution Window?

Choose each window from how long your own buyers take to act, and judge channels on signed customers in your CRM over your real sales cycle rather than on any window's count. Work through it in this order.

1. Measure your own timing. Pull recent customers from your CRM and note the time from first tracked click to lead, and from lead to signed deal, slow ones included.
2. List every report and the window behind it, from each Google conversion action, Meta ad set, LinkedIn conversion, Microsoft goal and GA4 property, and write the window on any report that goes to leadership.
3. Set click windows to cover the stage you count. If the platform counts form fills, cover the usual time from click to form fill, because stretching the window only to raise the count tells you nothing new.
4. Keep view windows short, for the reasons set out in What Is a View-Through Conversion?, and check LinkedIn's in particular, since its default view window is far longer than Google's or Microsoft's.¹²⁵
5. Send a qualified stage back when the sale closes after the window, such as a qualified lead or a booked site visit, through offline conversion imports that fit inside the platform's upload limit.⁷
6. Hold windows steady when comparing periods, and note the date of any change on the report, since changes apply only going forward.¹⁶
7. Judge channels on signed customers in your CRM over a period at least as long as your sales cycle, with the source recorded on every lead and a "How did you hear about us?" answer beside it.

If you're a smaller business with a short sales cycle and one or two channels, steps 1, 2 and 7 are most of the work, and a spreadsheet with a source column will do until a CRM is worth the cost.