Border with top triangle css Code Snippet in 2025

Creates a content container with a triangle at the top.

• Use the :before and :after pseudo-elements to create two triangles.
• The colors of the two triangles should be the same as the container's border-color and the container's background-color respectively.
• The border-width of the one triangle (:before) should be 1px wider than the other one (:after), in order to act as the border.
• The smaller triangle (:after) should be 1px to the right of the larger triangle (:before) to allow for its left border to be shown.

<div class="container">Border with top triangle</div>

.container {
  position: relative;
  background: #ffffff;
  padding: 15px;
  border: 1px solid #dddddd;
  margin-top: 20px;
}

.container:before,
.container:after {
  content: '';
  position: absolute;
  bottom: 100%;
  left: 19px;
  border: 11px solid transparent;
  border-bottom-color: #dddddd;
}

.container:after {
  left: 20px;
  border: 10px solid transparent;
  border-bottom-color: #ffffff;
}