What are attribution windows and why do they matter?

An attribution window is the time limit you place on how long after an email click a conversion can still be credited to that email. Most platforms let you set this: 24 hours, 7 days, 30 days.

Why it matters: purchase decisions don't always happen immediately. Someone clicks your email promoting a course, thinks about it for a week, and then buys. If your attribution window is 24 hours, you lose credit for that sale. If it's 30 days, you capture it.

But longer windows have a different problem: they can capture conversions that email didn't actually drive. A subscriber who clicked your email, forgot about it, and bought two weeks later because of a Google Ad sees that purchase credited to email in your analytics. Email gets the credit. The ad doesn't. Your ROI looks inflated, your ad performance looks deflated.

How to pick the right window: match it to your typical purchase cycle. If your product is a 20-euro impulse buy, a 24-48 hour window is probably right. If it's a 2,000-euro enterprise software subscription that takes weeks of evaluation, a 14-30 day window is more appropriate. Look at your actual conversion timing data if your platform shows it: how long after an email click do most conversions actually happen? That distribution tells you where to set the cutoff.

Most email platforms default to 7 days, which is a reasonable middle ground for many businesses. You can usually change it in your analytics settings if your purchase cycle is unusual.

Attribution windows interact with cross-device tracking too: if the click and conversion happen on different devices, the window may not even matter, because the connection between them is broken regardless. And if you're comparing email ROI to other channels, make sure they're all using the same window, otherwise the comparison is meaningless. ROI calculations can swing dramatically based on window length alone.