@wordpress/block-library/build-style/tab/style.css

Block library for the WordPress editor.

.wp-block-tab {
  box-sizing: border-box;
  color: inherit;
  display: block;
  width: max-content;
  text-decoration: none;
  cursor: pointer;
  flex-basis: inherit !important;
  flex-grow: inherit !important;
  position: relative;
  border: none;
  background: none;
  appearance: none;
  -webkit-appearance: none;
  margin: 0;
  padding: var(--wp--preset--spacing--20, 0.5em) var(--wp--preset--spacing--30, 1em);
  font-size: inherit;
  font-family: inherit;
  font-weight: inherit;
  line-height: inherit;
  letter-spacing: inherit;
  text-transform: inherit;
  text-align: inherit;
}
.wp-block-tab[aria-selected=true]::before, .wp-block-tab.is-active::before {
  content: "";
  position: absolute;
  border-bottom: 2px solid currentColor;
  pointer-events: none;
  left: 0;
  width: 100%;
  bottom: 0;
}