The weight of a typeface refers to the thickness of its strokes.

Within a typeface family, different weights are designed to be visually consistent across all glyphs of a given style.

NAMING CONVENTIONS

While much of the historical naming conventions (e.g., Light, Bold, Black) originate from the Latin typographic tradition, the concept of weight applies to all writing systems that use stroke thickness variations. These labels are not universal standards as style description conventions differs from a culture to another.

WEIGHT NAMES & CSS VALUES

In digital typography, weights are also expressed numerically, using the “font-weight attribute”:
• Thin: 100
• ExtraLight: 200
• Light: 300
• Regular: 400
• Medium: 500
• SemiBold: 600
• Bold: 700
• ExtraBold: 800
• Black: 900

FONT ENGINEERING HINT

In OpenType font formats, weight is stored in the OS/2 table under the “usWeightClass” field, which maps to CSS “font-weight” values (ranging from 100 to 900):
• while CSS defines nine steps, “usWeightClass” allows values from 1 to 1000, giving finer granularity for internal font definitions;
• CSS weight values are expected to correspond to the font’s weight class. Following this standard is important because many environments rely on these mappings for text rendering and style linking. If, for example, Regular = 350, browsers or apps may mislabel it or fail to recognize it as Regular, causing user confusion or incorrect transformation to Bold.

For variable fonts, the weight axis is defined by the registered axis tag “wght.” Unlike static fonts, it supports continuous interpolation between a minimum and maximum, allowing CSS “font-weight” to take any integer (e.g., 347) within the supported range for smoother transitions and precise control.

Localized weight names (e.g., ‘Gras’ for Bold in French, ‘Fett’ in German) are often generated from the OS’s internal dictionaries. This ensures style names appear in the user’s language even if the font lacks explicit translations. If the default naming does not strictly follow OpenType Specifications, localized names may not be translated correctly.