They are almost same. We usually use"但是“and”可是“. I think "但是"is stronger than”可是“.

可是 ＝ 但是 ＝ but 不过 ＝ 然而 ＝ however

可是 is a little more formal, softer and more common in the north of China than 但是. They can be shortened to 可 and 但 to make them more informal. 不过 is even more softer and informal. There's very little difference between them.

一样用法

When we translate "but", we can use anyone of them. So they are almost the same.