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ruby-position CSS property

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 to the right (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

Over example 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

Under example 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

Is a keyword indicating that the ruby annotation is placed to the right of the base text characters. This value is intended for bopomofo (zhuyin fuhao) ruby.

Formal definition

Initial valuealternate
Applies toruby annotation containers
Inheritedyes
Computed valueas specified
Animation typediscrete

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

See also

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