You can achieve this by adding the 'autocomplete=off' attribute to your input. You're going to need to create a frontend model and add it to your fields in the system.xml
NoAutoComplete.php (frontend model)
<?php
namespace Vendor\CustomModule\Model\Frontend;
class NoAutoComplete extends \Magento\Config\Block\System\Config\Form\Field
{
/**
@param \Magento\Framework\Data\Form\Element\AbstractElement $element
Output : return string
*/
protected function _getElementHtml(\Magento\Framework\Data\Form\Element\AbstractElement $element)
{
$html = '<input id="' . $element->getHtmlId() .
'" name="' . $element->getName() .
'" autocomplete="off" />';
return $html;
}
}
system.xml
<field id="credentials" translate="label" type="text" sortOrder="1" >
<label>Credentials</label>
<frontend_model>Vendor\CustomModule\Model\Frontend\NoAutoComplete</frontend_model>
</field>