ruby-position

Baseline 2024 *

Newly available

Since ⁨December 2024⁩, this feature works across the latest devices and browser versions. This feature might not work in older devices or browsers.

* Some parts of this feature may have varying levels of support.

The ruby-position CSS property defines the position of a ruby element relative to its base element. It can be positioned over the element (over), under it (under), or between the characters on their right side (inter-character).

Try it

ruby-position: over;

ruby-position: under;

<section id="default-example">
  <ruby id="example-element"> 明日 <rp>(</rp><rt>Ashita</rt><rp>)</rp> </ruby>
</section>

#example-element {
  font-size: 2em;
}

Syntax

css

/* Keyword values */
ruby-position: over;
ruby-position: under;
ruby-position: alternate;
ruby-position: alternate over;
ruby-position: alternate under;
ruby-position: inter-character;

/* Global values */
ruby-position: inherit;
ruby-position: initial;
ruby-position: revert;
ruby-position: revert-layer;
ruby-position: unset;

Values

over: Is a keyword indicating that the ruby has to be placed over the main text for horizontal scripts and right to it for vertical scripts.
under: Is a keyword indicating that the ruby has to be placed under the main text for horizontal scripts and left to it for vertical scripts.
alternate: Is a keyword indicating that the ruby alternates between over and under, when there are multiple levels of annotation.
inter-character: When specified, it behaves as over in vertical writing modes. Otherwise, it indicates that the ruby has to be placed between the different characters, appearing on the right of the base in horizontal text and forcing the children of the ruby annotation container to have a vertical-rl writing mode.

Formal definition

Initial value	`alternate`
Applies to	ruby annotation containers
Inherited	yes
Computed value	as specified
Animation type	discrete

Formal syntax

ruby-position = 
  [ alternate || [ over | under ] ]  |
  inter-character

Examples

Ruby positioned over the text

HTML

html

<ruby>
  <rb>超電磁砲</rb>
  <rp>（</rp><rt>レールガン</rt><rp>）</rp>
</ruby>

CSS

css

ruby {
  ruby-position: over;
}

Result

Ruby positioned under the text

HTML

html

<ruby>
  <rb>超電磁砲</rb>
  <rp>（</rp><rt>レールガン</rt><rp>）</rp>
</ruby>

CSS

css

ruby {
  ruby-position: under;
}

Result

Ruby alternate

HTML

html

<ruby>
  <rb>A</rb><rb>B</rb><rb>C</rb>
  <rtc>Above</rtc>
  <rtc>Below</rtc>
</ruby>

CSS

css

ruby {
  ruby-position: alternate; /* this is also the initial value */
}

Result

Specifications

Specification
CSS Ruby Annotation Layout Module Level 1 # rubypos

Browser compatibility

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This page was last modified on ⁨Jul 14, 2025⁩ by MDN contributors.

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