noun
non-white-space character; nonblank character
Computing term for any character that is not a space, tab, or other whitespace. Used in programming, text processing, and regular expressions.
この正規表現は非空白文字にマッチします。
This regular expression matches non-white-space characters.
パスワードには少なくとも一つの非空白文字が必要です。
The password must contain at least one non-white-space character.
空白文字 means 'white-space character' (space, tab, etc.), the opposite of 非空白文字.
Compound of 非 (non-) + 空白 (blank/white space) + 文字 (character). A straightforward technical term.