Theory on Hand Seals

[Stoopider]

Y THe Alien = Correct.

[SofaKing]

I think it's just too hard to animate the characters doing the hand seals each time, and would slow down the
fight. I think that the characters are still doing them, but they just aren't shown.

[kage_bunshin]

Personally i'm thinking that hand seals are only used for setting the user's chakra in a certain mode. Once the hand seals are performed, the chakra is 'set' to that mode. for e.g. 2 hours after the seals are done, the jutsu can be executed without doing the seals again.

I think thats why sasuke didn't need to redo the hand seal when doing chidori against itachi in ep84

This is just my opinion/theory though.

[SK]

i think you may be right, after a while you may know the jutsu so well that you dont need to concentrate your chakra so much. but i think sometimes they just do the hand seals really fast or with one hand sometimes like itachi. also i think the animators might just want to show the jutsu and you just have to assume the hand seals were performed.

[dragon]

hand seals show the element of the chakra ok athe hands seals that sasuke uses against garra are signs of the bird and dog and naruto is dog and frog itachi's hands are hidden under his jacket