Facebook on Friday announced that it's acquiring CrowdTangle, a service used by publishers including BuzzFeed, The New York Times and ESPN to optimize their content on social media.

The acquisition, which was made for an undisclosed sum, recognizes the growing importance of social optimization among publishers, according to a statement from a Facebook spokesperson.

“Publishers around the world turn to CrowdTangle to surface stories that matter, measure their social performance and identify influencers," the spokesperson said. "We are excited to work with CrowdTangle to deliver these, and more insights to more publishers."

With today's purchase, Facebook adds CrowdTangle's know-how and adds another layer to its relationship with publishers (CrowdTangle will continue to run its own product). It also has greater latitude to make improvements on CrowdTangle and invest directly in the company, which is presumably a win-win for both Facebook and its newly acquired asset.

In a blog post announcing the acquisition, CrowdTangle cited the "full support and resources of Facebook" as among the factors that made the deal attractive.

"Thanks to this partnership, our platform is only going to get more powerful," the statement reads. "All of our partners can not only expect the same quality of product, level of support, and pace of innovation they have come to expect from us, but they should and can expect even more from us going forward."

Facebook has worked with CrowdTangle in the past. Signal, the company's social listening service for journalists, incorporates CrowdTangle's technology to identify stories that are gathering momentum on Facebook. That relationship could deepen after today's acquisition.

Correction: A previous version of this story said CrowdTangle worked with The New York Post. In fact, it works with The New York Times.