Custom file input Bootsrap 4

In Bootstrap 4, the initial placeholder value is set in the custom-file-control with a pseudo CSS

Example

<div class="container">
            <div class="input-group mb-3">
                <div class="input-group-prepend">
                    <span class="input-group-text">Upload</span>
                </div>
                <div class="custom-file">
                    <input type="file" class="custom-file-input" id="inputGroupFile01">
                    <label class="custom-file-label" for="inputGroupFile01">Choose file</label>
                </div>
            </div>

            <div class="input-group mb-3">
                <div class="custom-file">
                    <input type="file" class="custom-file-input" id="inputGroupFile02">
                    <label class="custom-file-label" for="inputGroupFile02">Choose file</label>
                </div>
                <div class="input-group-append">
                    <span class="input-group-text" id="">Upload</span>
                </div>
            </div>

            <div class="input-group mb-3">
                <div class="input-group-prepend">
                    <button class="btn btn-outline-secondary" type="button">Button</button>
                </div>
                <div class="custom-file">
                    <input type="file" class="custom-file-input" id="inputGroupFile03">
                    <label class="custom-file-label" for="inputGroupFile03">Choose file</label>
                </div>
            </div>

            <div class="input-group">
                <div class="custom-file">
                    <input type="file" class="custom-file-input" id="inputGroupFile04">
                    <label class="custom-file-label" for="inputGroupFile04">Choose file</label>
                </div>
                <div class="input-group-append">
                    <button class="btn btn-outline-secondary" type="button">Button</button>
                </div>
            </div>
        </div>