Does flexbox work differently with items in an unordered list?

Question

I am trying to learn how to use flexbox and I am struggling with using it properly with an unordered list. I want the items inside to "spread out" in the container, but no matter what flex properties I apply they don't seem to work. Code below.

Why aren't the list items speading out within the container? All boxes, borders, and colors are for my own visual repesentation.

body {
  background-color: black;
  box-sizing: border-box;
}

header {
  display: flex;
  background-color: white;
  justify-content: space-between;
  align-items: center;
}

h1 {
  color: white;
  background-color: blue;
}

ul {
  background-color: blue;
  display: flex;
  list-style: none;
  justify-content: space-evenly;
}

li {
  border: 1px solid red;
}

<header>
  <div>
    <h1>Sample Logo</h1>
  </div>
  <div>
    <nav class="navbar">
      <ul>
        <li>Home</li>
        <li>Contacts</li>
        <li>Companies</li>
        <li>Calendar</li>
      </ul>
    </nav>
  </div>
</header>

Answer 1

the ul has padding. add some width to ul and the spacing will work

body {
  background-color: black;
  box-sizing: border-box;
}

header {
  display: flex;
  background-color: white;
  justify-content: space-between;
  align-items: center;
}

h1 {
  color: white;
  background-color: blue;
}

ul {
  border:solid 1px black;
  display: flex;
  width:50vw;
  
  list-style: none;
  justify-content: space-between;
}

li {
  border: 1px solid red;
}

<header>
  <div>
    <h1>Sample Logo</h1>
  </div>
  <div>
    <nav class="navbar">
      <ul>
        <li>Home</li>
        <li>Contacts</li>
        <li>Companies</li>
        <li>Calendar</li>
      </ul>
    </nav>
  </div>
</header>