Freddy’s Frozen Custard and Steakburgers is giving away free onion rings, but not for long.

Starting Saturday, June 22, the Kansas-based burger chain will treat fans to a free order of onion rings on National Onion Ring Day — so long as they have the mobile app.

No purchase is necessary.

Customers can redeem the one-time offer on the Freddy’s app until Monday, June 24.

The annual holiday celebrating the deep-fried snack falls on June 22.

Onion rings are said to have origins in Britain, where chef John Mollard wrote a recipe for “fried onions with Parmesan cheese” in his 1802 cookbook, according to NationalToday.com

“Mollard’s early onion rings weren’t all that different from the fried snack we enjoy today,” according to Back Then History. “His recipe … involved dipping half-inch-thick onion slices in batter, frying them in lard, and serving them with a side of mustard-spiked melted butter.”

Find your nearest Freddy’s here.

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