Tabi etiquette

Tabi (足袋) are traditional Japanese socks with a separation between the big toe and other toes.

In Takada Sensei's Dôjô almost all the students wear tabi during practice. Everyone can choose whether to wear them or not.

The only occasions when it's mandatory to wear tabi are when you're wearing montsuki (紋付). Those occasions are dan grading and iaidô demonstration.

In summer everyone wears white tabi but in winter some wear thicker and darker colored tabi. I guess the thicker ones are just warmer, I myself wear another socks under tabi in winter.

This is the tabi etiquette in Takada Sensei's Dôjô; other dôjô's, federation's, etc. style may vary.