C6 tuning (g, c, e, a) is the most popular ukulele tuning in the world today. Select this tuning if you're unsure which tuning to choose.
D6 tuning (a, d, f#, b) is a brighter-sounding ukulele tuning. Once common throughout Canada, Europe, and US, it is popular among teachers and those wanting to play with other stringed instruments (e.g. violin, banjo, mandolin, bass, guitar).