Shake Shack has rolled out its mobile ordering app for iOS nationwide after a trial period late last year. 

To celebrate the occasion, Shake Shack is giving a free single ShackBurger to each guest who downloads the Shack App, redeemable at any U.S. location (except airports, stadiums and ballparks) until Tuesday, Feb. 28.

To get the freebie, guests must download the app, create an account and use the promo code "shackappy" at checkout, according to a press release.

Shake Shack said several companies helped to create the app, including mobile product agency Fuzz, mobile ordering platform Olo, guest engagement platform Paytronix and digital experience testing services from Applause. An Android version of the app is in development, according to the announcement.