font-display

The font-display descriptor determines how a font face is displayed based on whether and when it is downloaded and ready to use.

Syntax

/* Keyword values */
font-display: auto;
font-display: block;
font-display: swap;
font-display: fallback;
font-display: optional;

Values

auto
The font display strategy is defined by the user agent.
block
Gives the font face a short block period and an infinite swap period.
swap
Gives the font face an extremely small block period and an infinite swap period.
fallback
Gives the font face an extremely small block period and a short swap period.
optional
Gives the font face an extremely small block period and no swap period.

Note

In Firefox, the preferences gfx.downloadable_fonts.fallback_delay and gfx.downloadable_fonts.fallback_delay_short provide the duration of the "short" and "extremely small" periods, respectively.

Description

The font display timeline

The font display timeline is based on a timer that begins the moment the user agent attempts to use a given downloaded font face. The timeline is divided into the three periods below which dictate the rendering behavior of any elements using the font face.

Font block period
If the font face is not loaded, any element attempting to use it must render an invisible fallback font face. If the font face successfully loads during this period, it is used normally.
Font swap period
If the font face is not loaded, any element attempting to use it must render a fallback font face. If the font face successfully loads during this period, it is used normally.
Font failure period
If the font face is not loaded, the user agent treats it as a failed load causing normal font fallback.

Formal definition

Related at-rule@font-face
Initial valueauto
Computed valueas specified

Formal syntax

[ auto | block | swap | fallback | optional ]

Examples

Specifying fallback font-display

@font-face {
  font-family: ExampleFont;
  src: url(/path/to/fonts/examplefont.woff) format('woff'),
       url(/path/to/fonts/examplefont.eot) format('eot');
  font-weight: 400;
  font-style: normal;
  font-display: fallback;
}

Specifications

Specification Status Comment
CSS Fonts Module Level 4
The definition of 'font-display' in that specification.
Working Draft Initial definition

Browser compatibility

BCD tables only load in the browser

See also