It's totally free and easy to use. Runs on any Unix [Linux, OSX] or Windows system.
Code:
youtube-dl -F "https://www.youtube.com/watch?v=DVwHCGAr_OE"
[youtube] DVwHCGAr_OE: Downloading webpage
[youtube] DVwHCGAr_OE: Extracting video information
[youtube] DVwHCGAr_OE: Downloading DASH manifest
[info] Available formats for DVwHCGAr_OE:
format code extension resolution note
171 webm audio only DASH audio 125k , audio@128k (44100Hz), 1.28MiB
140 m4a audio only DASH audio 127k , m4a_dash container, aac @128k (44100Hz), 1.40MiB
141 m4a audio only DASH audio 255k , m4a_dash container, aac @256k (44100Hz), 2.80MiB
278 webm 256x144 DASH video 93k , webm container, VP9, 12fps, video only, 856.29KiB
160 mp4 256x144 DASH video 111k , 12fps, video only, 1.18MiB
242 webm 426x240 DASH video 232k , 24fps, video only, 1.79MiB
133 mp4 426x240 DASH video 247k , 24fps, video only, 2.65MiB
243 webm 640x360 DASH video 436k , 24fps, video only, 3.29MiB
134 mp4 640x360 DASH video 611k , 24fps, video only, 3.87MiB
244 webm 854x480 DASH video 764k , 24fps, video only, 5.76MiB
135 mp4 854x480 DASH video 1119k , 24fps, video only, 7.49MiB
247 webm 1280x720 DASH video 1515k , 24fps, video only, 11.36MiB
136 mp4 1280x720 DASH video 2239k , 24fps, video only, 13.87MiB
248 webm 1920x1080 DASH video 2808k , 24fps, video only, 20.65MiB
137 mp4 1920x1080 DASH video 3718k , 24fps, video only, 24.75MiB
17 3gp 176x144
36 3gp 320x240
5 flv 400x240
43 webm 640x360
18 mp4 640x360
22 mp4 1280x720 (best)