An attribution model in Facebook Ads is the rule set that decides how credit for conversions gets assigned when users interact with your ads multiple times before completing a purchase or lead action. If someone sees your ad on Monday, clicks it Wednesday, and buys Friday, the attribution window determines whether Facebook counts that conversion or not. Facebook's standard attribution windows include 1-day click, 7-day click, and 1-day view. A 7-day click attribution model credits your ad for any conversion that happens within seven days of someone clicking it. The 1-day view model credits conversions that occur within 24 hours of someone viewing your ad, even if they never clicked. Since iOS 14.5 privacy changes in 2021, Facebook defaults to 7-day click and 1-day view combined, and you've lost access to longer windows like the old 28-day click. This matters enormously for budget allocation. If you sell higher-consideration products where people research for weeks, your campaigns will look less profitable under short attribution windows because you're missing delayed conversions. Conversely, if you run flash sales or impulse-buy products, 1-day windows show you tighter cause-effect relationships. The practical problem: Facebook's attribution data now conflicts with what you see in Google Analytics or your Shopify dashboard because each platform uses different models and tracking methods. Facebook counts conversions in its system even if the final purchase happened after someone Googled your brand name. Google Analytics gives last-click credit to Google. At Ottawa SEO, we tell clients to pick one source of truth for decision-making but cross-reference the others. For active Facebook advertisers, we typically use Facebook's reporting for in-platform optimization but reconcile total revenue monthly against Shopify or your actual bank deposits. Run your reports using consistent attribution settings, don't switch mid-campaign, and understand that your 7-day click ROAS is a modeled estimate, not Gospel truth. The attribution window you choose should match your actual sales cycle length as closely as Facebook's limited options allow.