Web/HTML/Element/sub

The HTML Subscript element () specifies inline text which should be displayed as subscript for solely typographical reasons. Subscripts are typically rendered with a lowered baseline using smaller text.

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Content categories	Flow content, phrasing content, palpable content.
Permitted content	Phrasing content.
Tag omission	None, both the starting and ending tag are mandatory.
Permitted parents	Any element that accepts phrasing content.
Implicit ARIA role	No corresponding role
Permitted ARIA roles	Any
DOM interface	`HTMLElement`

Attributes

This element only includes the global attributes.

Usage notes

The  element should be used only for typographical reasons—that is, to change the position of the text to comply with typographical conventions or standards, rather than solely for presentation or appearance purposes.

For example, using  to style the name of a company which uses altered baselines in their wordmark would not be appropriate; instead, CSS should be used (likely the vertical-align property, such as vertical-align: sub or, to more precisely control the baseline shift, vertical-align: -25%.

Appropriate use cases for  include (but aren't necessarily limited to):

Marking up footnote numbers. See Footnote numbers for an example.
Marking up the subscript in mathematical variable numbers (although you may also consider using a MathML formula for this). See Variable subscripts.
Denoting the number of atoms of a given element within a chemical formula (such as every developer's best friend, C₈H₁₀N₄O₂, otherwise known as "caffeine"). See Chemical formulas.

Examples

Footnote numbers

Traditional footnotes are denoted using numbers which are rendered in subscript. This is a common use case for :

<p>According to the computations by Nakamura, Johnson, and
Mason<sub>1</sub> this will result in the complete annihilation
of both particles.</p>

The resulting output looks like this:

Variable subscripts

In mathematics, families of variables related to the same concept (such as distances along the same axis) are represented using the same variable name with a subscript following. For example:

<p>The horizontal coordinates' positions along the X-axis are
represented as <var>x<sub>1</sub></var> ... <var>x<sub>n</sub></var>.</p>

The resulting output:

Chemical formulas

When writing a chemical formula, such as H₂0, the number of atoms of a given element within the described molecule is represented using a subscripted number; in the case of water, the subscripted "2" indicates that there are two atoms of hydrogen in the molecule.

Another example:

<p>Almost every developer's favorite molecule is
C<sub>8</sub>H<sub>10</sub>N<sub>4</sub>O<sub>2</sub>, which is
commonly known as "caffeine."</p>

The output:

Specifications

Specification	Status	Comment
HTML Living StandardThe definition of '<sub> and <sup>' in that specification.	Living Standard
HTML5The definition of '<sub> and <sup>;' in that specification.	Recommendation

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`sub`	Chrome Full support Yes	Edge Full support 12	Firefox Full support 1	IE Full support Yes	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support 4	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes

Legend

Full support: Full support