flex-fill

bootstrap5.css

.flex-fill {
  -ms-flex: 1 1 auto !important;
  flex: 1 1 auto !important;
}

html bootstrap5 Sample

flex幅を隙間をなくして伸縮均衡：flex-fill

flex文字01

flex文字

  <div class="d-flex">
    <div class="flex-fill">flex文字01</div>
    <div class="flex-fill">flex文字</div>
    <div class="flex-fill">flex文字</div>
  </div>