If you want a greater reduction in file size, you can make changes before you publish. Just open up Advanced Settings and lower the resolution or frame rate:
Adjust the frame rate.
Frame rate, measured in frames per second (fps), is usually 24 for film and 30 for television. For a standard YouTube video, the optimal rate is 29.97. Instagram requires a minimum of 30 fps, and YouTube allows for 24 fps. Lowering that rate will shrink the file size, but if your video captures a lot of movement, too low a frame rate will result in motion blur.
Adjust the resolution.
The optimal resolution for an HD YouTube video is 1080p. If you select 720p, you’ll decrease the video file size. Luckily, if your viewers are using phones, tablets, or laptops, they may not notice.