Although Shake Shack CEO Randy Gurutti spoke about the chain's partnership with Grubhub during last week's earnings call, he made the relationship official Thursday issuing a press release announcing the launch of nationwide delivery.

"As we begin our integrated partnership with Grubhub, we're focused on creating the best delivery experience for both our restaurant operators and our guests," Garutti said in the release. 

After various pilots, Shake Shack chose Grubhub as its exclusive partner, which means it's phasing out its partnerships with other third-party providers. The transition, Garutti admitted last week to investors, is affecting the chain's numbers. 

"We believe the transition to Grubhub caused some noise in our Q3 numbers and will certainly have an impact through the fourth quarter and into next year," Garutti said during the Nov. 4 call. "As we remove direct point-of-sale integrations with DoorDash, Postmates and Caviar, we expect an impact to our delivery revenue, especially in those regions where Grub may not be the current market leader. Any difference in pricing, placement or regional strength in non-Grub marketplaces will affect our sales for a period of time. How much volatility this will cause during this transitional period is uncertain, but the reality is this represents short- to mid-term revenue risk."

Shake Shack, however, is counting on help from Grubhub's enterprise support team, which Garutti said has dedicated resources for customer and operations support. In addition to leveraging the diner base of Grubhub's marketplace, the relationship will also leverage a data-sharing partnership, allowing both Shake Shack and Grubhub to reward loyal diners with special experiences and promotions throughout the year.

"We've been able to build out a deeply-integrated and robust partnership that positively impacts all parties, including the restaurant and our diners," Grubhub Founder and CEO Matt Maloney, said in the release. With the power of both brands, we're confident in our execution ahead and the large opportunity that this partnership represents for both Shake Shack guests and our diners."

To celebrate the launch, customers will receive free delivery through Nov. 17. Next month, Shake Shack and Grubhub will partner to bring diners in the Houston area an exclusive, invite-only music and culinary experience, according to the release.

Since the original Shack opened in 2004, in NYC's Madison Square Park, the company has expanded to more than 260 locations in 30 U.S. States and the District of Columbia, including more than 85 international locations across London, Hong Kong, Shanghai, Singapore, Philippines, Mexico, Istanbul, Dubai, Tokyo, Moscow and Seoul.