The font-variant-alternates property provides a way to request and control alternate glyphs that a typeface may offer beyond its default letterforms. Instead of changing weight, size, or the basic family, this property targets stylistic and contextual variations built into the font: alternate characters, swashes, contextual ligatures, and other designer-provided options. It acts as a higher-level, semantically meaningful interface for typographic alternates, allowing authors to express intent (for example, "use decorative alternates" or "prefer contextual forms") without dealing with low-level OpenType tag mechanics.

This property sits at a different abstraction level than lower-level feature controls. Authors who need precise control over specific OpenType features can use font-feature-settings, but that requires specifying feature tags and is more technical. Conversely, font-variant-alternates exposes named alternate behaviors in a more author-friendly way, letting the browser translate those names into the appropriate OpenType operations where supported. Because not all fonts implement every alternate, the property depends on the font’s internal design: if the requested alternates aren’t available, the browser will simply render the default glyphs.

In practice, font-variant-alternates is useful for typographic refinement - adding flair to headings, enabling context-sensitive character forms in text, or toggling decorative options for different design contexts - without swapping fonts. It also interacts with broader font handling: the actual alternates available are determined by the chosen font-family, and the property can be combined with other typographic controls such as font-variant to create comprehensive, accessible typographic styles. When designing with alternates, consider readability, consistency across platforms, and fallbacks, since alternate glyphs may differ in width or emphasis and can affect line breaks and layout.