HTML Entity - Ampersand

The ampersand (&) is one of the characters HTML treats as special. A raw ampersand can begin a character reference such as & or ©, so browsers may try to interpret it. In HTML text and inside attribute values, write & whenever you want a literal ampersand.

The symbol itself is a stylised ligature of the letters E and t, from the Latin word et, meaning "and". It was once recited as the 27th letter of the English alphabet, which is how the phrase "and per se and" eventually became the word ampersand.

Ampersands cause problems in several places at once: in HTML content, in attribute values such as links with more than one query parameter (?a=1&b=2), in XML and XHTML where a bare ampersand is a hard parse error, and in query strings where & is a parameter separator and must be percent-encoded as %26.

Encoding by context: in HTML content and attributes use &. In URL query strings and form data use %26. In JavaScript strings a literal & is fine, though some pipelines prefer the escape sequence. The numeric references & and & are equivalent to &.

Typical real-world cases are embedding a video or map URL that contains &, writing brand names such as "AT&T", and showing code samples on a page. Wrong encoding either silently drops query parameters (a broken link) or prints the wrong characters, for example a double-encoded & that renders as the text "&" instead of a single ampersand.

Because & is so common, escaping it correctly is one of the first habits of writing valid HTML and XML. It is also essential for safety: when user input is inserted into markup, correct escaping is part of what prevents injection attacks. If you are unsure which form to use, remember the rule of thumb: in markup use &, in URLs use %26, and everywhere else the raw & is usually correct.