The CSS anchor positioning module defines features that allow you to tether elements together. Certain elements are defined as anchor elements; anchor-positioned elements can then have their size and position set based on the size and location of the anchor elements to which they are bound.

In addition, the specification provides CSS-only mechanisms to:

• Specify a set of alternative positions for an anchored element; when the default rendering position causes it to overflow its containing block and/or be rendered offscreen, the browser will try rendering the anchored element in the alternative positions instead.
• Declare conditions under which anchor-positioned elements should be hidden, in situations where it is not appropriate to tether them to anchor elements.

Reference

Properties

• anchor-name
• position-anchor
• position-area
• position-try-fallbacks
• position-try-order
• position-try shorthand
• position-visibility

The CSS anchor positioning module also introduces the anchor-scope property. Currently, no browsers support this feature.

At-rules and descriptors

• @position-try

Functions

• anchor()
• anchor-size()

Data types and values

• anchor-center
• <anchor-side>
• <anchor-size>
• <position-area>
• <try-size>
• <try-tactic>

HTML attributes

• anchor Non-standard

Interfaces

• CSSPositionTryDescriptors
• CSSPositionTryRule
• HTMLElement.anchorElement Non-standard

Guides

Using CSS anchor positioning

An introductory guide to fundamental anchor positioning concepts, including associating, positioning, and sizing elements relative to their anchor.

Fallback options and conditional hiding for overflow

A guide to the mechanisms CSS anchor positioning provides to prevent anchor-positioned elements from overflowing their containing elements or the viewport, including position try fallback options and conditionally hiding elements.

Related concepts

• CSS logical properties and values module:
  • inset-block-start
  • inset-block-end
  • inset-inline-start
  • inset-inline-end
  • inset-block
  • inset-inline
  • inset shorthand
  • inline-size
  • min-block-size
  • min-inline-size
  • block-size
  • max-block-size
  • max-inline-size
  • margin-block
  • margin-block-end
  • margin-block-start
  • margin-inline
  • margin-inline-end
  • margin-inline-start
  • Inset properties glossary term
• CSS positioned layout module:
  • top
  • left
  • bottom
  • right
• CSS box model module:
  • width
  • height
  • min-width
  • min-height
  • max-width
  • max-height
  • margin
  • margin-bottom
  • margin-left
  • margin-right
  • margin-top
• CSS box alignment module:
  • align-items
  • align-self
  • justify-items
  • justify-self
  • place-items
  • place-self

Specifications

See also

• CSS scroll anchoring module
• Learn: CSS positioning
• CSS logical properties and values module
• Learn: Sizing items in CSS