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Preparing our partners for iOS 14: Mobile Web Advertising

Updated on April 26, 2021: On Tuesday, April 27, 2021 Facebook will begin rolling out new ad measurement protocols --Apple’s SKAdNetwork API and Facebook’s Aggregated Event Measurement -- following the release of iOS 14.5. Advertisers and partners will then begin to experience the changes described in this blog post. For the latest update visit the Facebook for Business blog.

Updated on April 21, 2021: On Tuesday, April 20, 2021, Apple confirmed that the release of general availability of iOS 14.5 will begin next week, and that it will start requiring apps in the App Store to obtain permission to “track” users across apps and websites owned by third parties for advertising and measurement purposes through it’s App Tracking Transparency (ATT) prompt. Apple’s prompt requirement will also prohibit certain data collection and sharing by businesses unless people opt in. As part of these changes, we’re implementing new ad measurement protocols, including Apple’s SKAdNetwork API and Facebook’s Aggregated Event Measurement and the changes described in this blog post will begin rolling out with the expected general availability of iOS 14.5 next week. We will provide an update with a specific date once more details are available from Apple. For the latest update, visit the Facebook for Business blog.

In June 2020, Apple announced a new iOS 14 AppTrackingTransparency framework, requiring apps to show a discouraging prompt, that will have hard hitting implications for businesses that advertise on mobile devices and across the web. We disagree with Apple's approach and solution. We understand how disruptive Apple’s changes may be to your business, and are committed to helping you manage through them.

In early 2021, Facebook will begin to show Apple’s App Tracking Transparency (ATT) prompt. Once Facebook and Instagram show Apple’s ATT prompt, those that optimize, target, and/or report on mobile web events from any of our business tools will be impacted given Apple’s required limits on data sharing.

Today, in order to help minimize disruption, we are providing you an update with our solutions that require actions you can take immediately, and actions you need to plan for in early 2021.


Aggregated Event Measurement: Facebook will introduce Aggregated Event Measurement to support measurement of web events from iOS 14 users once Apple requires the ATT prompt. It is designed to help you measure campaign performance in a way that is consistent with consumers’ decisions about their data.

Event Limits: You will be limited to the use of 8 conversion events per domain (i.e., 8 <pixel, event> or <custom conversion> per domain). You will not need to make changes to the pixel or your Conversions API implementation as event selection will be done in Events Manager beginning early 2021.

  • Ad sets optimizing for an event beyond the 8 that are prioritized will be paused.
  • The 8 conversion events per domain will be ranked based on priority. If multiple events are completed by a user (i.e. “add to cart” and “purchase”) only the higher prioritized event will be reported.
  • After the initial configuration, the domain owner will be able to configure which 8 events are tracked for a given domain in Events Manager.

Actions to take now:

Domain verification in Business Manager: We ask that you verify your domain using the steps outlined in the Facebook Help Center. This is critical for businesses with pixels used by multiple Business Managers or personal ad accounts. Domain verification will ensure no immediate or future disruption in the ability to configure conversion events.

Note: Domain Verification must be done at the effective top level domain plus one (eTLD+1 ). For example, for, and the eTLD+1 domain is

Plan for 8 conversion events per domain: If you use more than 8 conversion events per domain for optimization or reporting, prepare an action plan for how to operate with 8 conversion events per domain based on your business priorities. You will not need to make changes to the pixel or Conversions API implementation as event configuration will be done in Events Manager.



  • VO will transition from Ads Manager to Events Manager and value set will need to be enabled.
  • If you have previously used VO, value sets will be automatically assigned based on historical data and turned on in Events Manager.
  • If you are eligible and use VO infrequently or have never used it, value sets must be configured manually.
  • Turning on value sets will automatically utilize 4 out of the 8 events allowed for campaign optimization and reporting for a given domain. Advertisers will have the opportunity to allocate up to 8 event slots to value sets for greater precision.
  • For optimal performance, events with value sets turned on should be placed in higher priority slots within the Events Manager.

Actions to take now:


There are no specific changes for Dynamic Ads for Retargeting, but you may see performance and audience sizes decrease. We expect minimal impact to you using Dynamic Ads to reach Broad Audiences.

Actions to take now:

  • Verify product URL domains in the catalog feed and avoid the use of URLs redirecting users to a different domain.
  • Prepare to use only 1 pixel per catalog to optimize for prioritized conversion events across all catalog items.


Ads Reporting (Ads Manager, Ads Reporting, Ads Insights API):

  • 28-day click-through, 28-day view-through, and 7-day view-through attribution windows will not be supported. Historical data for these windows will remain accessible via the Ads Insights API.
  • Statistical modeling will be used for certain attribution windows and/or metrics to account for less data availability from iOS 14 users. In-product annotation will communicate when a metric is modeled.
  • Certain attribution windows will have partial reporting and metrics will not include all events from iOS 14 users. In-product annotation will communicate when a metric is partial. This will launch in early 2021.
  • Delivery and action breakdowns will not be supported for offsite conversion events.
  • Offsite conversion events will be reported based on the time the conversions occur and not the time of ad impressions. As a result, you may notice small fluctuations in cost metrics, as cost per conversion will reflect spend over a given period divided by conversions that took place over the same period, whereas today, cost per conversion reflects spend over a given period divided by conversions driven by ad impressions that took place over the same period.

Attribution Window Selection: We will be replacing the account-level attribution window with a new attribution setting at the ad set level that can be accessed during campaign creation. This attribution setting ensures that the conversions we measure are the same ones used to inform campaign optimization, and will allow for increased flexibility and clarity when analyzing ad performance. We will introduce a new API parameter to allow for the querying of results based on this new attribution setting.

For automated rules: In early 2021, attribution window settings for existing and newly created automated rules will no longer be supported, and a default window of 7-day click-through for non-iOS conversions and the SKAdNetwork window for iOS conversions will be implemented.

Actions to take now

Prepare for attribution window changes (deprecation of 28-day click-through, 28-day view-through, and 7-day view-through windows):

  • Adopt the Comparing Windows feature to see how conversions attributed to ads compare across different attribution windows. This allows you to better anticipate the impact to reported conversions as a result of upcoming attribution window changes.
  • Update any automated rules currently using a 28-day attribution window to prevent any unexpected adjustments in spend once the new 7-day click-through window default goes into effect.

DEVELOPER APIs (Marketing API, Ads Insights API, Targeting API)

Numerous Endpoint Changes: Our Marketing API, Ads Insights API, and Targeting API will have endpoint changes according to the changes referenced in the Event Management, Delivery, and Measurement sections of this document.

What you can do now

Take action on the changes mentioned in this blog, and review the changes coming to our APIs. These have not gone into effect and cannot be implemented at this time, however, we want to give you as much notice as possible. You can view the changelog here.

What you should plan for early 2021:

Implement API changes: We anticipate having API updates ready for implementation by mid-January of 2021, some of which may result in same day breaking changes. Technical information regarding API changes that will be required in early 2021 will be shared in our developer documentation.

For information on iOS 14 impact to App based developers please see our separate Developer blog post here.

For information on how to plan for changes to our Marketing API, please see our changelog.