CSS border-top-width Property

The border-top-width property is used to define the width of an element’s top border.

The width of the top border, as well as all the other border sides, can be defined with the border or border-width shorthand properties.

For setting the border-top-width you should first define the border-style property, because you need borders before setting its width. You can use either border-style or border-top-style to specify the border's style.

The specification doesn't define the exact thickness of each keyword. However, they always have the following order: thin ≤ medium ≤ thick.

The specification does not define how borders of different styles and width connect in the corners.

Initial Value	medium
Applies to	All elements. It also applies to ::first-letter.
Inherited	No
Animatable	Yes. The width of the border is animatable.
Version	CSS1
DOM Syntax	object.style.borderTopWidth = "5px";

Syntax

border-top-width: medium | thin | thick | length | initial | inherit;

Example of the border-top-width property:

<!DOCTYPE html>
<html>
  <head>
    <title>Title of the document</title>
    <style>
      p {
        padding: 8px;
        border-style: dotted;
        border-top-width: thick;
      }
    </style>
  </head>
  <body>
    <h2>Border-top-width example</h2>
    <p>As you can see the width of the top border is set to thick.</p>
  </body>
</html>

Try it Yourself »

Result

Example of the border-top-width property with all the values:

<!DOCTYPE html>
<html>
  <head>
    <title>Title of the document</title>
    <style>
      body {
        background: #ccc;
        font-size: 20px;
        text-align: center;
      }
      main div {
        display: flex;
        align-items: center;
        justify-content: center;
        color: black;
        padding-top: 30px;
        padding-bottom: 30px;
        width: 200px;
        height: 100px;
        margin: 15px;
        font-weight: bold;
        border: solid;
      }
      .flex-center {
        display: flex;
        justify-content: center;
      }
      /* border-top-width example classes */
      .b1 {
        border-top-width: medium;
      }
      .b2 {
        border-top-width: thin;
      }
      .b3 {
        border-top-width: thick;
      }
      .b4 {
        border-top-width: 10px;
      }
      .b5 {
        border-top-width: initial;
      }
      .b6 {
        border-top-width: inherit;
      }
    </style>
  </head>
  <body>
    <h1>Border-top-width value examples</h1>
    <main class="flex-center">
      <div class="b1">
        medium
      </div>
      <div class="b2">
        thin
      </div>
      <div class="b3">
        thick
      </div>
    </main>
    <main class="flex-center">
      <div class="b4">
        10px lenght
      </div>
      <div class="b5">
        initial
      </div>
      <div class="b6">
        inherit
      </div>
    </main>
  </body>
</html>

Try it Yourself »

Values

Value	Descriptions	Play it
medium	Defines medium top border. It is the default value of this property.	Play it »
thin	Defines a thin top border. It is up to the user agent to determine the exact width.	Play it »
thick	Defines a thick top border. It is up to the user agent to determine the exact width.	Play it »
length	Defines the the thickness length of the top border. For example, 10px, 5em, 8pt, etc.	Play it »
initial	Sets the property to its default value.	Play it »
inherit	Inherits the property from its parent element.