The ideal length for a promotional video generally ranges from 60 to 90 seconds for optimal engagement, with most successful promos being under 120 seconds to align with limited audience attention spans. While shorter videos (15-30 seconds) are effective for ads and social media, longer formats (up to 6 minutes) can be suitable for YouTube videos to build communities and explore topics in depth. A professional youtube marketing agency aims for around 60-90 seconds for better engagement.