What changes is Facebook making to web campaign measurement?

In addition to the changes Facebook is implementing for app install campaigns on iOS 14, they have also announced updates for their web campaign measurement (specifically, ads shown in the Facebook mobile app on iOS 14 that lead to a website).

While we don't currently believe Facebook's web campaigns changes will impact a typical advertiser's use of Branch (see Can Branch links still be used in Facebook web campaigns? and Will Branch support PCM or AEM? for more details), we recognize that many customers also use Facebook for web campaigns outside of Branch. To help, we're sharing some of the information we've seen:

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Guidance from Facebook on web campaign changes

Collected from a Facebook communication shared on Twitter

What we know:

• This is an industry-wide shift for the digital advertising ecosystem though different companies are approaching it differently
• Facebook will be adopting Apple's prompt as we have no real choice but to
• We will be issuing a pre-prompt notification and are currently in public testing here
• Opt out users will go through FB's AEM (Aggregated Event Measurement). The data we receive will be different for opt-out versus other users but for consistency many features will be impacted across the board, outlining some of the big ones:
  • Attribution will change, since for opt out users Apple is provide data that is restricted, delayed, and aggregated; 28-click, 28-day view, and 7-day view attribution will no longer be available
  • Historical data for these windows will still be available but through the Ads Insights API
  • AEM only supports 1-day click attribution window currently.
  • 1-day click data will be modeled to estimate conversions from iOS users; Landing Page View will also use statistical modeling
  • 7-day click and 1-day view data will be partial and not be modeled at this time
• Conversion events will be reported at the time of conversion, not the time of impression
• The new default for Ads Manager is 7-day click attribution after enforcement from the current default of 7-day click 1-day view; All existing ad set settings will be maintained, but new ad sets will be on 7-day click unless you change it
• All web advertisers are restricted to using only 8 events for optimization
• If an advertiser wants to optimize for value, this would take up 4
• 1-day view and 7-day click will have partial data as it will not include opted out users
• Conversion tracking by age, gender, region and placement will be unavailable
• Targeting using 1st party data like age, gender, geo, etc. will not be impacted
• Users who opt-out will not be able to be added to custom audiences and exclusions
• Upper funnel campaigns and Brand Lift tracking will be mostly unimpacted including Lead Ads, Video View Ads, etc.

What we think we know, but will need to test:

• Bid cap will likely be the bidding tactic many advertisers lean on
• We may need to think about setting bids for a week, rather than a day
• Due to signal loss and less signal we may need to broaden audiences or we may need to do more targeting depending on optimization power
• Due to lowered conversion volume with a shorter optimization window we may need to segment less
  (have less ad sets)

What we don't know:

• The exact timeline of when this will happen, "early Spring" is still all we have
• Opt-out rates, these will likely never be shared
• How much performance will be impacted, highly likely to vary by advertiser
• How products like value optimization and cost cap will function in the world
• The impact on audiences like Lookalikes and Value-Based Lookalikes and Custom Audiences
• What learning phase means in the new world
• How to quantify the additional value beyond what we can see in the limited new view