font-weight

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

The font-weight CSS property sets the weight (or boldness) of the font. The weights available depend on the font-family that is currently set.

Try it

Syntax

css
/* <font-weight-absolute> keyword values */
font-weight: normal;
font-weight: bold;

/* <font-weight-absolute> numeric values [1,1000] */
font-weight: 100;
font-weight: 200;
font-weight: 300;
font-weight: 400; /* normal */
font-weight: 500;
font-weight: 600;
font-weight: 700; /* bold */
font-weight: 800;
font-weight: 900;

/* Keyword values relative to the parent */
font-weight: lighter;
font-weight: bolder;

/* Global values */
font-weight: inherit;
font-weight: initial;
font-weight: revert;
font-weight: revert-layer;
font-weight: unset;

The font-weight property is specified using either a <font-weight-absolute> value or a relative weight value, as listed below.

Values

normal

Normal font weight. Same as 400.

bold

Bold font weight. Same as 700.

<number>

A <number> value between 1 and 1000, both values included. Higher numbers represent weights that are bolder than (or as bold as) lower numbers. This allows fine-grain control for variable fonts. For non-variable fonts, if the exact specified weight is unavailable, a fallback weight algorithm is used — numeric values that are divisible by 100 correspond to common weight names, as described in the Common weight name mapping section below.

lighter

One relative font weight lighter than the parent element. Note that only four font weights are considered for relative weight calculation; see the Meaning of relative weights section below.

bolder

One relative font weight heavier than the parent element. Note that only four font weights are considered for relative weight calculation; see the Meaning of relative weights section below.

Fallback weights

If the exact weight given is unavailable, then the following rule is used to determine the weight actually rendered:

  • If the target weight given is between 400 and 500 inclusive:

    • Look for available weights between the target and 500, in ascending order.
    • If no match is found, look for available weights less than the target, in descending order.
    • If no match is found, look for available weights greater than 500, in ascending order.

  • If a weight less than 400 is given, look for available weights less than the target, in descending order. If no match is found, look for available weights greater than the target, in ascending order.

  • If a weight greater than 500 is given, look for available weights greater than the target, in ascending order. If no match is found, look for available weights less than the target, in descending order.

Note: The fallback weight algorithm is only used for rendering. The computed value of the property is still the specified value.

Meaning of relative weights

When lighter or bolder is specified, the below chart shows how the absolute font weight of the element is determined.

Note that when using relative weights, only four font weights are considered — thin (100), normal (400), bold (700), and heavy (900). If a font family has more weights available, they are ignored for the purposes of relative weight calculation.

Inherited value bolder lighter
100 400 100
200 400 100
300 400 100
400 700 100
500 700 100
600 900 400
700 900 400
800 900 700
900 900 700

Common weight name mapping

The numerical values 100 to 900 roughly correspond to the following common weight names (see the OpenType specification):

Value Common weight name
100 Thin (Hairline)
200 Extra Light (Ultra Light)
300 Light
400 Normal (Regular)
500 Medium
600 Semi Bold (Demi Bold)
700 Bold
800 Extra Bold (Ultra Bold)
900 Black (Heavy)
950 Extra Black (Ultra Black)

Variable fonts

While many fonts have a particular weight corresponding to one of the numbers in Common weight name mapping, most variable fonts support a range of weights providing much finer granularity, giving designers and developers more control over the chosen weight.

For TrueType or OpenType variable fonts, the "wght" variation is used to implement varying widths.

This demo loads with font-weight: 500; set. Change the value of the font-weight property to see the weight of the text change.

Accessibility

People experiencing low vision conditions may have difficulty reading text set with a font-weight value of 100 (Thin/Hairline) or 200 (Extra Light), especially if the font has a low contrast color ratio.

Formal definition

Initial valuenormal
Applies toall elements and text. It also applies to ::first-letter and ::first-line.
Inheritedyes
Computed valuethe keyword or the numerical value as specified, with bolder and lighter transformed to the real value
Animation typea font weight

Formal syntax

font-weight = 
  <font-weight-absolute>  |
  bolder                  |
  lighter                 

<font-weight-absolute> = 
  normal             |
  bold               |
  <number [1,1000]>

Examples

Setting font weights

HTML

html
<p>
  Alice was beginning to get very tired of sitting by her sister on the bank,
  and of having nothing to do: once or twice she had peeped into the book her
  sister was reading, but it had no pictures or conversations in it, "and what
  is the use of a book," thought Alice "without pictures or conversations?"
</p>

<div>
  I'm heavy<br />
  <span>I'm lighter</span>
</div>

CSS

css
/* Set paragraph text to be bold. */
p {
  font-weight: bold;
}

/* Set div text to two steps heavier than
   normal but less than a standard bold. */
div {
  font-weight: 600;
}

/* Set span text to be one step lighter
   than its parent. */
span {
  font-weight: lighter;
}

Result

Specifications

Specification
CSS Fonts Module Level 4
# font-weight-prop

Browser compatibility

BCD tables only load in the browser

See also