bootstrap4.css
.custom-range {
  width: 100%;
  height: calc(1rem + 0.4rem);
  padding: 0;
  background-color: transparent;
  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none;
}
bootstrap4.css
.custom-range:focus {
  outline: none;
}
bootstrap4.css
.custom-range:focus::-webkit-slider-thumb {
  box-shadow: 0 0 0 1px #fff, 0 0 0 0.2rem rgba(0, 123, 255, 0.25);
}
bootstrap4.css
.custom-range:focus::-moz-range-thumb {
  box-shadow: 0 0 0 1px #fff, 0 0 0 0.2rem rgba(0, 123, 255, 0.25);
}
bootstrap4.css
.custom-range:focus::-ms-thumb {
  box-shadow: 0 0 0 1px #fff, 0 0 0 0.2rem rgba(0, 123, 255, 0.25);
}
bootstrap4.css
.custom-range::-moz-focus-outer {
  border: 0;
}
bootstrap4.css
.custom-range::-webkit-slider-thumb {
  width: 1rem;
  height: 1rem;
  margin-top: -0.25rem;
  background-color: #007bff;
  border: 0;
  border-radius: 1rem;
  transition: background-color 0.15s ease-in-out, border-color 0.15s ease-in-out, box-shadow 0.15s ease-in-out;
  -webkit-appearance: none;
  appearance: none;
}
bootstrap4.css
@media (prefers-reduced-motion: reduce) {
  .custom-range::-webkit-slider-thumb {
    transition: none;
  }
}
bootstrap4.css
.custom-range::-webkit-slider-thumb:active {
  background-color: #b3d7ff;
}
bootstrap4.css
.custom-range::-webkit-slider-runnable-track {
  width: 100%;
  height: 0.5rem;
  color: transparent;
  cursor: pointer;
  background-color: #dee2e6;
  border-color: transparent;
  border-radius: 1rem;
}
bootstrap4.css
.custom-range::-moz-range-thumb {
  width: 1rem;
  height: 1rem;
  background-color: #007bff;
  border: 0;
  border-radius: 1rem;
  transition: background-color 0.15s ease-in-out, border-color 0.15s ease-in-out, box-shadow 0.15s ease-in-out;
  -moz-appearance: none;
  appearance: none;
}
bootstrap4.css
@media (prefers-reduced-motion: reduce) {
  .custom-range::-moz-range-thumb {
    transition: none;
  }
}
bootstrap4.css
.custom-range::-moz-range-thumb:active {
  background-color: #b3d7ff;
}
bootstrap4.css
.custom-range::-moz-range-track {
  width: 100%;
  height: 0.5rem;
  color: transparent;
  cursor: pointer;
  background-color: #dee2e6;
  border-color: transparent;
  border-radius: 1rem;
}
bootstrap4.css
.custom-range::-ms-thumb {
  width: 1rem;
  height: 1rem;
  margin-top: 0;
  margin-right: 0.2rem;
  margin-left: 0.2rem;
  background-color: #007bff;
  border: 0;
  border-radius: 1rem;
  transition: background-color 0.15s ease-in-out, border-color 0.15s ease-in-out, box-shadow 0.15s ease-in-out;
  appearance: none;
}
bootstrap4.css
@media (prefers-reduced-motion: reduce) {
  .custom-range::-ms-thumb {
    transition: none;
  }
}
bootstrap4.css
.custom-range::-ms-thumb:active {
  background-color: #b3d7ff;
}
bootstrap4.css
.custom-range::-ms-track {
  width: 100%;
  height: 0.5rem;
  color: transparent;
  cursor: pointer;
  background-color: transparent;
  border-color: transparent;
  border-width: 0.5rem;
}
bootstrap4.css
.custom-range::-ms-fill-lower {
  background-color: #dee2e6;
  border-radius: 1rem;
}
bootstrap4.css
.custom-range::-ms-fill-upper {
  margin-right: 15px;
  background-color: #dee2e6;
  border-radius: 1rem;
}
bootstrap4.css
.custom-range:disabled::-webkit-slider-thumb {
  background-color: #adb5bd;
}
bootstrap4.css
.custom-range:disabled::-webkit-slider-runnable-track {
  cursor: default;
}
bootstrap4.css
.custom-range:disabled::-moz-range-thumb {
  background-color: #adb5bd;
}
bootstrap4.css
.custom-range:disabled::-moz-range-track {
  cursor: default;
}
bootstrap4.css
.custom-range:disabled::-ms-thumb {
  background-color: #adb5bd;
}
■フォーム:form-group:コンポーネント:カスタムレンジ入力

  <form>
    <div class="form-group mb-5">
      <label for="formControlRange">レンジ入力の例</label>
      <input type="range" class="form-control-range" id="defaultRange"> </div>
    <div class="form-group mb-5">
      <label for="customRange1">カスタムレンジ入力の例</label>
      <input type="range" class="custom-range" id="customRange1"> </div>
    <div class="form-group mb-5">
      <label for="customRange2">カスタムレンジ入力の例(min="0",max="5")</label>
      <input type="range" class="custom-range" min="0" max="5" id="customRange2"> </div>
    <div class="form-group mb-5">
      <label for="customRange3">カスタムレンジ入力の例(step="0.5")</label>
      <input type="range" class="custom-range" min="0" max="5" step="0.5" id="customRange3"> </div>
  </form>