Left Square Bracket [

The Left Square Bracket character ([) is a standard HTML entity defined in the HTML specification. In HTML source code, it can be written using the named entity reference [, the decimal numeric character reference [, or the hexadecimal numeric reference [. The character is assigned Unicode code point U+005B in the Universal Character Set.

The left square bracket is used in programming for array indexing, markdown link syntax, regular expressions, and mathematical interval notation. While it does not typically need escaping in HTML text content, it may conflict with markdown parsers or certain template systems.

Technical character entities represent brackets, delimiters, and punctuation marks that frequently require escaping in HTML source code and programming contexts. Characters like curly braces, square brackets, pipes, and backslashes often carry special meaning in templating engines, regular expressions, or markup parsers, making their explicit HTML entity encoding important for preventing unintended interpretation by the browser or build tools.

When deciding how to encode the Left Square Bracket character in your HTML documents, the named entity [ is generally the most readable choice for developers reviewing or maintaining source code. The decimal form [ and hexadecimal form [ are equally valid alternatives that work in contexts where named entities may not be supported, or when generating HTML output programmatically from server-side code. All three representations produce identical visual output in every modern web browser.

Use the left square bracket entity when the literal [ character might be interpreted as markdown syntax (links, images) or regular expression character class notation. It is useful in technical documentation that mixes HTML with content that uses bracket-based syntax.