Is it necessary to use alt="" ?
also according to w3c regulations,alt=" " is now important to have for your code to be validated properly.
It is necessary if you want everyone to know.
Yes, its necessary. Because if theres a problem opening or reading the image, then its better to have a text version of it, than to have nothing.
use alt="" attribute. you want everyone to know what it is and that it's there.
alt image help search engine to know what image content (Google image search)