CSS entries starting with “O”

Every CSS entry starting with O, grouped by kind. Pseudo-classes, pseudo-elements and types are filed by their first letter, ignoring the leading :, :: or <.

Name	Description
Color
`oldlace`	Named colour #fdf5e6.
`olive`	Named colour #808000.
`olivedrab`	Named colour #6b8e23.
`orange`	Named colour #ffa500.
`orangered`	Named colour #ff4500.
`orchid`	Named colour #da70d6.
Container feature
`orientation`	Whether the query container is portrait or landscape.
Descriptor
`override-colors`	An @font-palette-values descriptor replacing palette colours by index.
Function
`oklab()`	A colour in the perceptually even OKLab space.
`oklch()`	A colour from lightness, chroma and hue in the OKLCH space.
`opacity()`	A filter that makes an element more transparent.
Media feature
`orientation`	Whether the viewport is portrait or landscape.
`overflow-block`	How block-axis overflow is handled: none, scroll or paged.
`overflow-inline`	Whether inline-axis overflow can be scrolled.
Property
`object-fit`	How an image or video is sized to fit its box.
`object-position`	Where an image or video sits inside its box.
`object-view-box`	Crops a replaced element's content to a chosen rectangle.
`offset`	Shorthand that places a box on a motion path.
`offset-anchor`	The point of a box that sits on its motion path.
`offset-distance`	How far along its motion path a box sits.
`offset-path`	The path a box is placed on.
`offset-position`	The starting point of a motion path such as ray().
`offset-rotate`	Which way a box faces on its motion path.
`opacity`	Makes an element and its contents partly transparent as one group.
`order`	Moves a flex or grid item earlier or later in the visual order.
`orphans`	The fewest lines of a paragraph left at the bottom of a page or column.
`outline`	Shorthand for a line drawn outside the border that takes up no space.
`outline-color`	The colour of the outline.
`outline-offset`	The gap between the border edge and the outline.
`outline-style`	The line style of the outline, or auto for the browser focus ring.
`outline-width`	The thickness of the outline.
`overflow`	Shorthand for what happens when content is bigger than its box.
`overflow-anchor`	Opts an element out of scroll anchoring.
`overflow-block`	Overflow handling along the block axis.
`overflow-clip-margin`	How far clipped content may paint outside its box.
`overflow-inline`	Overflow handling along the inline axis.
`overflow-wrap`	Lets an overlong word break to avoid overflow. Formerly word-wrap.
`overflow-x`	Overflow handling in the horizontal axis.
`overflow-y`	Overflow handling in the vertical axis.
`overlay`	Whether an element is in the top layer; transitioned to delay its removal.
`overscroll-behavior`	Shorthand for scroll chaining and overscroll effects at a container's edge.
`overscroll-behavior-block`	Overscroll behaviour in the block axis.
`overscroll-behavior-inline`	Overscroll behaviour in the inline axis.
`overscroll-behavior-x`	Overscroll behaviour in the horizontal axis.
`overscroll-behavior-y`	Overscroll behaviour in the vertical axis.
Pseudo-class
`:only-child`	Matches an element with no sibling elements.
`:only-of-type`	Matches an element with no siblings of the same type.
`:open`	Matches an open details, dialog, or select or input with its picker showing.
`:optional`	Matches form controls that are not required.
`:out-of-range`	Matches an input whose value is outside its min and max.
Type
`<overflow-position>`	safe or unsafe: what alignment does when an item overflows.
`<overflow>`	The overflow keywords: visible, hidden, clip, scroll and auto.