chromium/chrome/test/data/dlp/file_paste.html

<!-- Page to help with testing of copy and paste of files.
    Input is at (0,0) to (500,500) coordinates. -->

<!doctype html>

<head>
    <meta charset="utf-8">
    <style>
        div {
            position: absolute;
            left: 0px;
            background: green;
            top: 0px;
            width: 500px;
            height: 500px;
            border: 0px;
            margin: 0px;
            padding: 0px;
        }
    </style>
    <script type="text/javascript">
        window.onload = function () {
            document.getElementById("pasteTarget").
                addEventListener("paste", async (e) => {
                    try {
                        let file = e.clipboardData.items[0].getAsFile();
                        const content = await file.text();
                        console.log(content);
                    } catch {
                        console.log("Could not read the file.");
                    }
                });
        };
    </script>
</head>

<body>
    <div id="pasteTarget">
        Paste here.
    </div>
</body>

</html>