What's the difference between Hubspot's conversion tracking feature and Conversions?

Hubspot's Ad Optimization Event feature does not support Facebook's conversion optimization system and will not protect your performance from iOS 14.5.

The Ad Optimization Event feature uses an old API that Facebook released back in May 2018, called the Offline Conversions API.

The API is designed for reporting, specifically for offline events (like in-store purchases).

Although the name is similar, the Offline Conversions API is different than Facebook's new Conversion API and is not a replacement for the features that protect your performance from iOS 14.5, ad blockers, and other cookie-blocking privacy tools.

Offline Conversion API vs Conversion API

Facebook's confusing naming practice is unfortunate, because using the wrong API will have a material impact on your ad performance.

Facebook's Offline Conversions API (which should not be mistaken for the new Conversions API) will not help your ads performance in a cookieless world.

Facebook uses a separate system to process conversion events that are used for performance optimization, which is powered by the Conversion API.

If you are not using the Conversion API (or a product that integrates with the the API, like Clearbit Conversions) you should expect to lose conversion data and suffer poorer performance across Facebook and Instagram as systems like Apple and Google begin restricting cookie-based tracking methods.

The Conversion API fuels your Facebook ad performance

The distinction between these two APIs is important.

The recent changes in conversion tracking (like Apple's iOS 14.5 update) are not concerning because they impact reporting.

Even though lost conversion data will impact reporting, most B2B advertisers measure performance by passing UTM parameters to their marketing automation platform, or using an attribution tools like Bizible or Attribution.

More importantly, lost conversion data will hurt ad performance... reducing conversion volume and increasing cost.

To understand why, it helps to understand why we care about conversion data in the first place.


The primary purpose of sending conversion data is to train Facebook's machine learning algorithms to understand what actions you want your audience to take, so that it can predict who is most likely to take that action if they show an ad.

In other words, the Conversion API fuels Facebook's ability to generate high-quality results at a low cost.

Unfortunately, the Offline Conversion API is not compatible with Facebook conversion optimization system (which is why they released the Conversion API).

Can I still track offline conversions? Absolutely. The Conversion API support both online and offline conversion events. In fact, it makes an improvement on the old system by providing a way to optimize for both types of events within the same campaign.

For example, if one prospect inbounds via email and another inbounds by filling out your demo request form, Facebook will be able to attribute both conversions back to any ads that influenced those actions.

Clearbit + Conversion API ❤️

Clearbit Conversions allows you to integrate your Hubspot data directly with the Conversions API, which allows you to send both offline and online events server-side, and fuels your Facebook ad performance with high-quality conversion data.

Learn how Clearbit Conversions protects and improves your Facebook ad performance →