Facebook today announced that it has purchased CrowdTangle, a 4-year-old tool that publishers use to track how content spreads around the web, for an undisclosed sum. By showing its subscribers a kind of real-time pulse of the web, CrowdTangle has developed an outsized but mostly hidden influence on the stories you see popping up in your news feeds throughout the day. The move shows Facebook is continuing to court publishers at a time of continuing uncertainty about how to build sustainable, profitable businesses when most news is consumed on platforms that publishers don’t own.

Facebook says it will continue to invest in and operate the service so that more publishers could take advantage of it. CrowdTangle’s small, distributed team, which had raised about $2.2 million from investors including Betaworks, will continue to lead development of the product. “Publishers around the world turn to CrowdTangle to surface stories that matter, measure their social performance and identify influencers,” Facebook said in a statement. “We are excited to work with CrowdTangle to deliver these, and more insights to more publishers.”

As detailed in a profile last year in FastCompany, CrowdTangle was originally designed as a tool to help activists organize their Facebook activity into a single place. But there was no money in that, so co-founders Brandon Silverman and Matt Garmur took a feature that showed which posts on their pages were getting the most engagement and turned it into a product. The result was a dashboard that any publisher could use to see what was working — and what wasn’t — on Facebook, Twitter, Instagram, and (RIP) Vine.

Tools like CrowdTangle explain the eerie sameness on the web

Soon it was being used by big publishers including BuzzFeed, the Huffington Post, CNN, USA Today, ESPN, MTV, and (yes) The Verge. It’s also used by brands (L’Oreal Paris) and nonprofits (Greenpeace). Among other things, tools like CrowdTangle explain the eerie sameness you find on much of the web these days. When every publisher can see that a zero-effort post on the latest Game of Thrones trailer is outperforming everything else on a competitor’s site, soon every site is posting the latest Game of Thrones trailer.

CrowdTangle joins Facebook’s existing publisher analytics tools, which include Signal (for discovering which news stories are trending) and Page Insights (which offer analytics tools for pages.) “Thanks to this partnership, our platform is only going to get more powerful,” CrowdTangle’s founders said in a blog post. “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.”