A complete sentence like that would nornally have a “subject” - in this case it should refer to me in the “second person” by using “you”. Failing to refer to me as the subject makes the sentence incomplete and seem informal. The sentence literally does not respect me.
Such informality would usually only be used in conversation with a friend or acquaintance. It’s jarring to me to see that in written English, especialy coming from a computer.
A more formal and complete sentence would be: “Do you want to save this file?” That’s formal and not rude, but if you want to be more polite you’d say : “Would you like to save this file?”
I can’t really explain why “Would you like . . .?” is more polite than “Do you want . . . ?”, it just is in my experience. Perhaps that’s not globally true though many might disagree.
FYI since you’re asking about English, “no rude” would normally be written as “non-rude” or you can just use the opposite word “polite”.