ZeroDays is Ireland's largest CTF. Running since 2015, it has grown to be the largest on-site, one-day CTF in the world. In 2023 over 130 teams of four competed with over 500 competitors in total. The event has three categories for Irish colleges, Irish schools and an Open section for any team to enter.

International competitors welcome but be aware that this is an in-person event! Expect a wide range of challenges suitable for all skill levels; plenty of easy challenges for newer players and some extremely difficult challenges for more experienced players.

Prizes are awarded to the top 3 players in each category (SCHOOLS, COLLEGE + OPEN).