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).

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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

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 valuealternate
Applies toruby annotations 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

Report problems with this compatibility data on GitHub
desktopmobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
ruby-position
alternate
Experimental
inter-character
over
under

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support
Partial support
Partial support
No support
No support
Experimental. Expect behavior to change in the future.
See implementation notes.
Requires a vendor prefix or different name for use.
Has more compatibility info.

See also