This matches any ASCII character (codes 0–127).

This matches any letter or digit. For multibyte characters, it matches characters whose Unicode ‘general-category’ property (see Character Properties) indicates they are alphabetic or decimal number characters.

This matches any letter. For multibyte characters, it matches characters whose Unicode ‘general-category’ property (see Character Properties) indicates they are alphabetic characters.

This matches horizontal whitespace, as defined by Annex C of the Unicode Technical Standard #18. In particular, it matches spaces, tabs, and other characters whose Unicode ‘general-category’ property (see Character Properties) indicates they are spacing separators. (If you only need to look for ASCII whitespace characters, we suggest using an explicit set of character alternatives, such as ‘[ \t]’, instead, as it will be faster than [[:blank:]].)

This matches any character whose code is in the range 0–31.

This matches ‘0’ through ‘9’. Thus, ‘[-+[:digit:]]’ matches any digit, as well as ‘+’ and ‘-’.

This matches graphic characters—everything except spaces, ASCII and non-ASCII control characters, surrogates, and codepoints unassigned by Unicode, as indicated by the Unicode ‘general-category’ property (see Character Properties).

This matches any lower-case letter, as determined by the current case table (see The Case Table). If case-fold-search is non-nil, this also matches any upper-case letter. Note that a buffer can have its own local case table different from the default one.

This matches any multibyte character (see Text Representations).

This matches any non-ASCII character.

This matches any printing character—either spaces or graphic characters matched by ‘[:graph:]’.

This matches any punctuation character. (At present, for multibyte characters, it matches anything that has non-word syntax, and thus its exact definition can vary from one major mode to another, since the syntax of a character depends on the major mode.)

This matches any character that has whitespace syntax (see Table of Syntax Classes). Note that the syntax of a character, and thus which characters are considered “whitespace”, depends on the major mode.

This matches any unibyte character (see Text Representations).

This matches any upper-case letter, as determined by the current case table (see The Case Table). If case-fold-search is non-nil, this also matches any lower-case letter. Note that a buffer can have its own local case table different from the default one.

This matches any character that has word syntax (see Table of Syntax Classes). Note that the syntax of a character, and thus which characters are considered “word-constituent”, depends on the major mode.

This matches the hexadecimal digits: ‘0’ through ‘9’, ‘a’ through ‘f’ and ‘A’ through ‘F’.