When you practice writing kanji, use the form in the video or under "stroke order".
Typical Japanese serif fonts are called 明朝体, and sans-serif fonts are called ゴシック体. They are very common, but do not necessarily reflect how you should write characters by hand. (By the way, this is not specific to Japanese; many English serif fonts use "double-story g", which is not what people typically write by hand.)
There is a font called 教科書体 (literally "textbook font"), which is used in children's textbooks and reflects how people should handwrite characters. For more information, see: Is there an "official" font or other writing standard that should be used when teaching kanji?