McDonald's is treating its app users to free medium fries every Friday until the end of 2023. Customers who are part of the rewards program and make a minimum $1 purchase can take advantage of the offer at participating locations once each Friday. To qualify for the promotion, users must download the McDonald's mobile app, create an account, and enroll in the rewards program. The free fries promotion runs every single Friday from October 27th to December 29th.