Fluid typography is the practice of letting font sizes scale proportionally with the viewport rather than jumping between fixed values at media query breakpoints. The core tool is CSS clamp(), which takes a minimum, a preferred, and a maximum value; the preferred value is typically a viewport-width expression that interpolates smoothly between the two bounds.

Adrian Bece’s breakdown covers the math in detail: the preferred parameter is derived from a linear equation relating viewport width to font size, and using rem units for the min and max values (rather than px) preserves browser-level text zoom, which is critical for accessibility. Without that adjustment, fluid sizing can override a user’s default font-size preference and fail WCAG criteria.

Amit Sheen’s argument for breakpoint-free UI treats fluid typography as one piece of a larger shift: intrinsic CSS primitives like clamp(), container queries, and container units should handle the continuous adaptation work, while media queries are reserved for device capabilities and user preferences. Under this model, fluid type is not a workaround but the default approach.

Fluid sizing interacts directly with type selection. Font pairing references that preview combinations at specific sizes assume static sizing; when type scales fluidly, pairing choices need to hold up across a range rather than at a single set point. The two concerns are separable in code but linked in practice.