`ruby-position` CSS property

Baseline Newly available

This feature works across the latest devices and browser versions. This feature might not work in older devices or browser versions. It's been available across browsers since December 2024.

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

/* 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

This property is specified as one of the following keyword 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: 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 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

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

CSS

ruby {
  ruby-position: over;
}

Result

Ruby positioned under the text

HTML

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

CSS

ruby {
  ruby-position: under;
}

Result

Ruby alternate

HTML

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

CSS

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

Result

Specifications

Specification
CSS Ruby Annotation Layout Module Level 1 # rubypos

Browser compatibility

	Desktop					Mobile
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on iOS	Samsung Internet	WebView Android	WebView on iOS
`ruby-position`	84 1 Implemented as a non-standard, prefixed, version of `ruby-position`, `-webkit-ruby-position`: it has two properties: `before` and `after` (both equivalent, for ltr and rtl scripts to the standard `over` value used with `ruby-align: start`).	84 79 Implemented as a non-standard, prefixed, version of `ruby-position`, `-webkit-ruby-position`: it has two properties: `before` and `after` (both equivalent, for ltr and rtl scripts to the standard `over` value used with `ruby-align: start`). 12–79	38	70 15 Implemented as a non-standard, prefixed, version of `ruby-position`, `-webkit-ruby-position`: it has two properties: `before` and `after` (both equivalent, for ltr and rtl scripts to the standard `over` value used with `ruby-align: start`).	18.2 7 Implemented as a non-standard, prefixed, version of `ruby-position`, `-webkit-ruby-position`: it has two properties: `before` and `after` (both equivalent, for ltr and rtl scripts to the standard `over` value used with `ruby-align: start`).	84 18 Implemented as a non-standard, prefixed, version of `ruby-position`, `-webkit-ruby-position`: it has two properties: `before` and `after` (both equivalent, for ltr and rtl scripts to the standard `over` value used with `ruby-align: start`).	38	60 14 Implemented as a non-standard, prefixed, version of `ruby-position`, `-webkit-ruby-position`: it has two properties: `before` and `after` (both equivalent, for ltr and rtl scripts to the standard `over` value used with `ruby-align: start`).	18.2 7 Implemented as a non-standard, prefixed, version of `ruby-position`, `-webkit-ruby-position`: it has two properties: `before` and `after` (both equivalent, for ltr and rtl scripts to the standard `over` value used with `ruby-align: start`).	14.0	84 4.4 Implemented as a non-standard, prefixed, version of `ruby-position`, `-webkit-ruby-position`: it has two properties: `before` and `after` (both equivalent, for ltr and rtl scripts to the standard `over` value used with `ruby-align: start`).	18.2 7 Implemented as a non-standard, prefixed, version of `ruby-position`, `-webkit-ruby-position`: it has two properties: `before` and `after` (both equivalent, for ltr and rtl scripts to the standard `over` value used with `ruby-align: start`).
`alternate`	No	No	88	No	No	No	88	No	No	No	No	No
`inter-character`	84 This value is only supported with the prefixed version of the property.	84 This value is only supported with the prefixed version of the property.	No	70 This value is only supported with the prefixed version of the property.	18.2 Safari positions `inter-character` ruby to the right of the base character, but does not correctly position tone marks for bopomofo (Zhuyin Fuhao) annotations.	84 This value is only supported with the prefixed version of the property.	No	60 This value is only supported with the prefixed version of the property.	18.2 Safari on iOS positions `inter-character` ruby to the right of the base character, but does not correctly position tone marks for bopomofo (Zhuyin Fuhao) annotations.	14.0 This value is only supported with the prefixed version of the property.	84 This value is only supported with the prefixed version of the property.	18.2 WebView on iOS positions `inter-character` ruby to the right of the base character, but does not correctly position tone marks for bopomofo (Zhuyin Fuhao) annotations.
`over`	84	84	38	70	18.2	84	38	60	18.2	14.0	84	18.2
`under`	84	84	38	70	18.2	84	38	60	18.2	14.0	84	18.2

`ruby-position` CSS property

Try it

Syntax

Values

Formal definition

Formal syntax

Examples

Ruby positioned over the text

HTML

CSS

Result

Ruby positioned under the text

HTML

CSS

Result

Ruby alternate

HTML

CSS

Result

Specifications

Browser compatibility

See also