HDOR or 100 Days of Running is a lifestyle application available on Android designed to encourage people to make running a part of their daily routine. The program is developed by GSS Pvt Ltd and is available for free in the Health & Fitness category.

The application is a fitness movement that started in 2015 with a goal to promote running as a habit towards better fitness. The 2020 edition of the program is set to begin on May 1st, and it is expected to have more than 50,000 runners from India and around the world commit to running daily through the hottest months of summer. This event is by far the largest multi-day running challenge in the world. Joining the challenge is easy with the HDOR app, and users can track their progress and share their achievements with others.