How to get free fries from McDonald's, Wendy's, and other restaurants on National French Fry Day

• McDonald's, Wendy's, and other chains are offering up free french fries on July 13.
• Most of the fry deals require that you download the chains' apps, and in some cases make another purchase.

National French Fry Day is Wednesday, July 13, and some major chains are offering deals for the holiday.

Major chains including McDonald's and Wendy's are using the french fry offer as a way to push more customers towards their mobile apps. Rewards programs have become nearly essential for fast food chains to attract and keep customers. These programs have proven to be hugely advantageous for chains as they incentivize return visits and give companies valuable customer data. You'll have to join rewards programs to receive many of the deals listed here.

Here are the deals, and how to get them:

McDonald's

McDonald's will give all customers a free order of large fries on Wednesday as long as they order in the McDonald's app. There is no purchase necessary for the free order, McDonald's said in a press release.

Wendy's

Wendy's is offering an entire week of french fry deals for National Fry Day. On Wednesday, Wendy's fans can get any size fry with any mobile order. Thursday's deal is focused on breakfast potatoes, which will be free with any mobile order. Finally, on Friday customers who order fries through the Wendy's app can also get a free medium fry, Wendy's shared in a press release.

White Castle

White Castle will give customers a free small fry with any purchase using coupon code "FRYDAY," the chain shared online.

Burger King

Burger King has a long-running french fry promotion, and it will also be available for the holiday. Burger King Royal Perks Members can get a free fry of any size with a mobile order. The offer is available every week for the rest of the year, though it can only be used once each week.

Do you have a story to share about a retail or restaurant chain? Email this reporter at mmeisenzahl@businessinsider.com.