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The HTML <sub> element defines a span of text that should be displayed, for typographic reasons, lower, and often smaller, than the main span of text.

Content categories Flow content and phrasing content
Permitted content Phrasing content
Tag omission None, both the starting and ending tag are mandatory.
Permitted parents Any element that can contain phrasing content
Permitted ARIA roles Any
DOM Interface HTMLElement


This element only includes the global attributes.

Usage notes

  • This element should be used for typographical reasons only, i.e. changing the position of the text changing its meaning like in mathematical (like t2, though the use of a MathML formula should be considered) or chemical formulas (like H2O).
  • This element must not be used for styling purpose like the styling of the product name Latex. In that case CSS style should be used: the vertical-align property with the sub value will achieve the same effect.


<p>The chemical formula of water: H<sub>2</sub>O</p>


The chemical formula of water: H2O


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

See also

  • The <sup> HTML element that produces superscript. Note that you cannot use them both at the same time and you need to use MathML to produce both a superscript and a subscript next to the chemical symbol of an element, representing its atomic number and its nuclear number.
  • The <msub>, <msup>, and <msubsup> MathML elements.

Document Tags and Contributors

 Last updated by: mfluehr,