CSS: “font-style”: “bold” is not a “font-style” value.

The font-style and font-weight properties serve different purposes. font-style controls whether text appears in a normal, italic, or oblique style, while font-weight controls how thick or thin the characters are rendered. Writing font-style: bold is a mistake because bold is not among the accepted values for font-style. Browsers will ignore the invalid declaration entirely, meaning your text won’t become bold at all — it will simply render in the default weight.

This error typically comes from confusing the two properties or misremembering which property handles boldness. The valid values for each property are:

• font-style: normal, italic, oblique, or oblique with an angle (e.g., oblique 10deg)
• font-weight: normal, bold, bolder, lighter, or numeric values from 100 to 900

To fix this issue, replace font-style: bold with font-weight: bold. If you intended to make text both bold and italic, you’ll need to use both properties separately.

Examples

Incorrect — using bold with font-style

This triggers the validation error because bold is not a valid font-style value:

<p style="font-style: bold;">This text won't actually be bold.</p>

Correct — using font-weight for boldness

Move the bold value to the font-weight property:

<p style="font-weight: bold;">This text is bold.</p>

Correct — combining bold and italic

If you want text that is both bold and italic, use both properties:

<p style="font-weight: bold; font-style: italic;">This text is bold and italic.</p>

Correct — using font-weight in a stylesheet

You can also apply bold styling through a <style> block or external stylesheet, using either keyword or numeric values:

<style>
  .emphasis {
    font-weight: bold;
  }
  .light {
    font-weight: 300;
  }
  .heavy {
    font-weight: 900;
  }
</style>

<p class="emphasis">This text is bold (weight 700).</p>
<p class="light">This text is light (weight 300).</p>
<p class="heavy">This text is extra heavy (weight 900).</p>

Note that the keyword bold is equivalent to the numeric value 700, and normal is equivalent to 400. Numeric values give you finer control over text weight, especially when using variable fonts or font families that offer multiple weight variations.

Learn more:

MDN Reference

MDN: font-style

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MDN Reference

MDN: font-weight

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