Double Prime ″

The Double Prime 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+2033 in the Universal Character Set.

The double prime symbol represents inches in imperial measurements, arcseconds in angular measurement, and second derivatives in mathematics. It consists of two prime marks and should not be replaced with a straight quotation mark. Correct use of the double prime is essential in technical, scientific, and geographic content.

Punctuation and whitespace entities are among the most frequently used HTML entities in web development. They handle characters that either have special meaning in HTML syntax — such as angle brackets and ampersands — or represent typographic characters that improve the visual quality of text, like em dashes and curly quotes. Proper use of punctuation entities is essential for producing valid, well-formed HTML documents and achieving professional-looking typography on the web.

When deciding how to encode the Double Prime 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 double prime for inches (6″), arcseconds in geographic coordinates (40° 26′ 46″ N), and second derivatives in calculus (f″). Like the single prime, it should not be substituted with quotation marks. Using the correct character ensures accurate rendering in technical documentation.