Should your video be 3 minutes or 15 minutes? Tell us about your content, and we'll recommend the optimal length.
YouTube doesn't strictly favor long or short videos; it favors "Total Watch Time" and "Relative Retention". A 10-minute video with 50% retention (5 mins watch time) is generally better than a 3-minute video with 80% retention (2.4 mins watch time). However, making a video longer than it needs to be will bore viewers and hurt your retention.
The best video length is exactly as long as it takes to deliver the promised value—and not a second longer. If you can explain something in 5 minutes, don't stretch it to 10 just for more ad revenue, as viewers will drop off and the algorithm will penalize the video.