[mitemte]

Maybe something like this, which relies solely on flex box for layout.

    .outer { 
      display: flex;
      justify-content: space-between;
      align-items: center;
    }

    .left {
      flex: 1;
      display: flex;
      justify-content: flex-start;
    }

    .middle {
      flex: 1;
      display: flex;
      justify-content: center;
    }

    .right {
      flex: 1;
      display: flex;
      justify-content: flex-end;
    }

[meindnoch]

Wrong. `flex: 1` will cause the items to have a max-width of 1/3rd the container width. E.g. if the left and right items are small icons, and the middle one is a longer text, then the text will be forced to wrap into multiple lines as soon as it tries to grow beyond 1/3rd of the available space, even though there's tons of wasted space on the left/right.