Conversion attribution windows in bidding

What is the conversion window?

The conversion window is the length of time between an ad click or view and when Facebook counts a conversion from the user. In bidding and ad delivery context, the conversion window defines which conversions are taken into account when optimizing your ad delivery.

Based on the settings, conversions that happen within 1 or 7 days of the ad click or 1-day view are used to optimize the ad delivery. Only the KPI with this attribution window is minimized — so don't be surprised if you optimize towards click-through only and do not get optimal click+view-through results!

Note! Changing the conversion window parameter is only available with the OFFSITE_CONVERSIONS optimization goal.

Attribution Window vs. Conversion Window

In reporting, it is called the Attribution Window. You can see your ads' results with any combination of 1/7/28 days of click or view-through attribution. This means that an Ad gets credit for the conversion if the user last clicked or saw this specific ad (clicks get precedence) and the conversion also happened within the specified number of days after the impression.

In bidding, a similar concept is called the Conversion Window. The choices are more limited than in reporting, but the principle is similar: Facebook will optimize the cost of conversions that happen within the specified conversion window. If you choose the bid conversion window of 1-day click-through, Facebook will deliver to those people who are most likely to convert within 24 hours after clicking the ad. The conversion window of course also affects how low or high your Bid Cap should be: you can bid more for 1-day click-through conversions than 7-day click-through conversions (since the attributed CPA will always be lower when measured with a longer window).

How do I know which Conversion Window I should use?

To make the decision, consider in this priority order:

• Use a Conversion Window that provides enough data for Facebook's optimization
• Use a Conversion Window that captures mostly incremental conversions and not the others

Start by changing your attribution window and see how that affects the number of conversions reported in your campaigns. Choose a timeframe that is well in the past: for example, for a 28-day attribution window, the numbers can still grow up to 28 days after the impression happened. Therefore, choose a timeframe that is at least a month long but also exclude the past month.

Note: if you check, for example, 7-day click or view-through conversions of a running campaign, look at historical data — exclude the past 7 days. This is because there will be more conversions coming in for the Ad impressions shown yesterday. The data is only "mature" when 7 days have passed since the Ad delivery. This phenomenon also explains why the CPA graph often looks like it is skyrocketing in the past few days with long conversion windows.

Check especially the windows available in bidding: 1-d click, 7-day click, 1-day click + 1-day view, and 7-day click + 1-day view. You will probably see that the number of conversions is higher with longer windows, and when including view-through. Also, notice how your CPA behaves: it likely decreases with bigger windows. This means your Bid Cap should very much take the conversion window into account!

How much data is enough for bidding?

Facebook's conversion optimized bidding requires some data to work properly. The official recommendation varies, but a good rule of thumb is to have at least 25 conversions per week per Ad Set. If your Ad Sets don't generally get these many conversions, use a longer conversion window and include view-through if possible. This will help Facebook find more people who are likely to convert.

If you have enough conversions, move to the next section.

Use the Time to Conversion view to analyze customer behavior

Read about this in more detail on the Time to Conversion view article.

For bidding, the idea is to use a conversion window that mimics incrementality. In other words, choose a conversion window that captures people who converted because of your Ads, not just sometime after seeing them. See if you have a "spike" in the graph on days 0 and 1 and if you have a large "baseline" of conversions that happen long after the impression. Then choose a window that captures the spike but not the baseline. This will help Facebook find more people who are likely to convert because of seeing your ads! Read more.

When can I use which conversion windows?

This depends on your campaign objective, optimization goal, and promoted object (website or app).

• In a Conversions or Catalog Sales (dynamic ads) campaign
  • with the Offsite Conversions optimization goal, promoting a website, you can use:
    • 1-day click-through
    • 7-day click-through
    • 1-day click-through or 1-day view-through
    • 7-day click-through or 1-day view-through
  • with the App Events optimization goal, promoting a mobile app, you can use:
    • 1-day click-through
    • 1-day click-through or 1-day view-through
• In an App Installs campaign
  • with the App Installs optimization goal, you can use:
    • 1-day click-through
    • 1-day click-through or 1-day view-through
  • with the App Events optimization goal, you can use:
    • 1-day click-through
    • 7-day click-through
• In a Link Clicks campaign, with the Offsite Conversions optimization goal, you can use:
  • 1-day click-through
  • 7-day click-through