“Video engagement” as a KPI has finally gone mainstream. It went from being a more abstract concept to becoming a tangible click, download, social share, game, quiz, sign-up, purchase, “view more,” or any other direct, voluntary interaction with a brand’s video ad.

Because engagement is now concrete and quantifiable, it is directly responsible for a number of measurable outcomes that lead to increased data around viewability, time earned, awareness, and more.

Here are five reasons advertisers across all screens should factor engagement into their list of target KPIs:

1. Engagement ensures viewability.

Viewability and verification are crucial metrics for advertisers, but they’re not always measured accurately. For instance, brands may confirm that a video ad was served to a specific IP address without knowing whether or not it was actually viewed. Without an opportunity for video engagement, all that is certain is that the ad was delivered, not that it was seen.

Giving viewers the opportunity to actively participate with your brand by adding content, quizzes, social media integrations, content downloads, or even the opportunity to buy your product on the spot, without leaving the ad unit helps to clarify this confusion. Not every user will interact with the video, but brands will know a lot more about the ones who do.

2. Engagement rate is more telling than completion rate.

“Completion” simply means that a video played the entire way through, uninterrupted. In the past, advertisers have often perceived completion as engagement, but whether the viewer truly engaged is something that advertisers can only really know if there’s something with which to engage. Completion rates may give advertisers data, but they can’t answer the question, “why?”

3. Engagement means more data.

For data to be valuable, it needs to lead to reliable and actionable conclusions. It’s important to implement some sort of engagement to obtain knowledge about what resonates with customers as a whole and individually. Advertisers can then use this data to optimize their videos to be more tailored to their audience’s specific preferences.

One example of this could be a TV network running a promotional video featuring clips of footage from some of its most popular shows, with a button to “launch the trailer” accompanying each clip. Based on the trailer the viewer launches, the advertiser now knows which show(s) the viewer is interested and can serve future ads accordingly.

4. Engagement gets customers to act—and even buy—in real time.

With video, customers are no longer interested in operating on a long timeline; they expect seamless engagement or buying in real-time. Advertisers’ goals should be to make a connection with customers and give them the opportunity to either engage or buy in that exact same moment.

5. Engagement means you spend more time with customers and they spend less time with someone else.

If your audience already seems to know everything there is to know about your product, you can hold their attention by using the tools you have to let them interact with your product in the most entertaining and inviting ways possible. The goal is to lead them to the buying opportunity quicker.

Thanks to all of the interaction that’s now possible through advanced video marketing, engagement is not just a standard KPI that predicts what audiences might do, it tells us what they are actually doing and have done.

For more information about engagement and other key video metrics, download our 2016 Global Video Benchmarks report.