A regex character class defines a set of characters to match. It includes custom classes using square brackets [] and predefined classes like d, w, and s.

[a-z] matches lowercase letters, [0-9] matches digits, and [^abc] matches any character except a, b, or c. Predefined classes d (digits), w (word characters), and s (whitespace) are frequently used. Regex pattern guides cover character class usage.

Unicode-aware regex supports property escapes like p{Script=Hiragana} to match characters from specific scripts or categories.

Inside character classes, most metacharacters are treated as literals, but ], , ^ (at start), and - (range) retain special meaning. Text processing automation books demonstrate practical regex-based text processing.