How do I prefill the email address?

Use our API method set-option to set the “feedback_values” property:

Saber.do('set_option', 'feedback_values', {
    'Email': 'john@example.com'
});

Here’s a complete example of the Saber Feedback snippet, with email prefilled:

<!-- Saber Feedback button -->
<script type="text/javascript">
    (function () {
        window.Saber = {
            apiKey: '[YOUR API KEY HERE]',
            com:[],do:function(){this.com.push(arguments)}
        };
        var e = document.createElement("script");
        e.setAttribute("type", "text/javascript");
        e.setAttribute("src", "https://widget.saberfeedback.com/v2/widget.js");
        document.getElementsByTagName("head")[0].appendChild(e);
        Saber.do('set_option', 'feedback_values', {
            'Email': 'john@example.com'
        });
    })();
</script>
<!-- End of Saber Feedback button -->