"321 Football" in the UK generally refers to a specialized, small-sided 3v3 (three-versus-three) football format aimed at young players, specifically Under-7s (U7s) as part of the England Football "Future Fit" initiative. This format is designed to increase engagement, technical skill, and fun for children, with plans for it to become the mandated format for U7s from the 2026/27 season.