Syntax Updated November 2026

Escaping special characters

These characters need a backslash to be matched literally: . * + ? ^ $ ( ) [ ] { } | \ and, in a JavaScript literal, the slash. A price like $4.99 is \$4\.99. Fewer characters are special inside a character class. Escape user input before building a pattern from it.

Syntax

\.  \*  \+  \?  \^  \$  \(  \)  \[  \]  \{  \}  \|  \\  \/

Examples

"Costs $4.99 or $4x99".match(/\$4\.99/g)

Result: ["$4.99"]

Without the backslashes, $ means end of string and . means any character.

"1+1=2".replace(/\+/, " plus ")

Result: "1 plus 1=2"

const esc = s => s.replace(/[.*+?^{}$()|[\]\\]/g, "\\$&");
new RegExp("^" + esc("a.b*c") + "$").test("a.b*c")

Result: true

Escape user input before putting it in a pattern; newer engines offer RegExp.escape().

new RegExp("\\d+\\.\\d+").test("3.14")

Result: true

In a string the backslash itself must be doubled.

Common mistakes

Leaving the dot unescaped: a.b matches axb and a b as well as a.b.
Passing a string with single backslashes to new RegExp: "\d" becomes "d" before the regex sees it; write "\\d".
Forgetting to escape / in a JavaScript literal, which ends the regex early and throws a SyntaxError.
Dropping raw user input into new RegExp, so a search for "c++" throws and "." matches everything.

Practice Escaping special characters

These drills check your answer on live data, free, no account needed.

Escaping: a price like $4.99The whole line must match. Match a dollar sign, one or more digits, a period and exactly two digits.
Currency amounts with commasThe whole line must match. Match a dollar amount: $, then 0 or a number without leading zeros that uses a comma every three digits (so $1,234, never $1234), then optionally a period and exactly two digits of cents.
Lookbehind: amounts after $Match every amount that comes right after a dollar sign: digits with optional two-digit cents. The whole match is compared, so it must not include the $.

Questions

How do I match a literal backslash?

Escape it: \\ in the pattern. In a JavaScript or Python string without raw syntax that becomes "\\\\" (four backslashes).

How do I match a dollar sign in regex?

\$ matches a literal dollar. Inside a character class, [$] works without the backslash.

Do I need to escape a hyphen or a slash?

A hyphen only inside a character class when it is not first or last. A slash only inside a JavaScript regex literal; in strings and in other languages it is a normal character.

Character classesWhat a character class matches, how ranges and negation work, what \d \w \s and their uppercase opposites mean, and what the dot does and does not match.
Negated character classHow [^...] matches any character except the listed ones, stripping non-digits, grabbing quoted text, splitting on a delimiter, and how it differs from (?!).
Regex for URLA URL regex for validation and for pulling links out of text, capturing scheme, host, port and path, avoiding trailing punctuation, and when to use new URL.
match, test, replace in JavaScriptWhich JavaScript regex method to use for a yes/no check, the first match, all matches with groups, substitution and splitting, with return values and g rules.