Problem
By default, ‘website’ fields in Gravity Forms will display a validation error message if the user enters an address that is missing the protocol – HTTP, HTTPS, FTP.
The script below will check the value submitted before it is validated and add HTTP:// if it is missing.
If you want to verify the URL as well see — Gravity Forms – ‘Please enter a valid Website URL’ validation error when value missing protocol HTTP HTTPS FTP

Solution
The code below will:
- check for ‘website’ fields in a submitted form
- if the field value does not include a protocol – assume it is http:// and automatically add it to the value
To install the code either add it to your theme’s functions.php file, below the opening <?php line or create your own custom functions plugin and add it there.
add_filter( 'gform_pre_render', 'itsg_check_website_field_value' );
add_filter( 'gform_pre_validation', 'itsg_check_website_field_value' );
function itsg_check_website_field_value( $form ) {
foreach ( $form['fields'] as &$field ) { // for all form fields
if ( 'website' == $field['type'] || ( isset( $field['inputType'] ) && 'website' == $field['inputType']) ) { // select the fields that are 'website' type
$value = RGFormsModel::get_field_value($field); // get the value of the field
if (! empty($value) ) { // if value not empty
$field_id = $field['id']; // get the field id
if (! preg_match("~^(?:f|ht)tps?://~i", $value) ) { // if value does not start with ftp:// http:// or https://
$value = "http://" . $value; // add http:// to start of value
}
$_POST['input_' . $field_id] = $value; // update post with new value
}
}
}
return $form;