Twitter users will soon be able to tag tweets with exact locations. Reuters

Foursquare, the social app that popularized the check-in, is partnering with Twitter to allow users to add location data to tweets. Now users can choose to add location to tweets using Foursquare data, which includes businesses, landmarks, streets or other locations.

The deal is a lifeline for Foursquare, which claims 50 million users but has pivoted from just social check-ins to a service for social discovery. The deal will potentially expose many of Twitter's 288 million users to Foursquare data within tweets.

Twitter users have been able to add Foursquare location to tweets for awhile now, but only by using the "Swarm" app, which split off from the original Foursquare app last year. Twitter has its own location function, but it's not as accurate or specific as Foursquare's. Now Twitter users can tag tweets with a city, neighborhood, intersection or business, through the new feature powered by Foursquare’s API, Twitter explained in a blog post and geo-tagged a tweet from its headquarters:

In a world where we can share what we're doing at every moment, Twitter has made it even easier to share where we're doing it. Imagine if Twitter had released this update last night, we could have known exactly where Ted Cruz announced his presidential run.

Beyond being a useful tool for Twitter users, the partnership is a clear indication of where Foursquare sees itself headed as a geo-location app turned discovery and data service. Launched in 2009, Foursquare originated as a mobile app by which users could check in at local businesses, compete for mayorships, and earn discounts and prizes.

However, in May 2014, Foursquare overhauled its check-in features and split into two apps. The original Foursquare app was optimized for providing nearby restaurant recommendations, more like a Yelp service. The new app Swarm served just for check-ins.

This transition angered some users who cherished mayorships and saw no need for another Yelp. Some questioned whether the company could survive. But as Fortune reported, Foursquare oversees a ton of specific location data that can be useful not only to consumers but also to businesses as they can boast high user numbers.

Foursquare founder Dennis Crowley elaborated on that data-driven mission via a Medium post Monday, after Twitter’s announcement. Crowley shared that Foursquare has nearly 85,000 partners that already use its location API. These include big tech companies like Microsoft, Pinterest, Samsung, and now, Twitter.