Validation
Bootstrap Custom styles
Custom feedback styles apply custom colors, borders, focus styles, and background
icons to better communicate feedback. Background icons for <select>s are
only available with .form-select, and not .form-control.
Validation Tooltips
If your form layout allows it, you can swap the .{valid|invalid}-feedback classes for
.{valid|invalid}-tooltip classes to display validation feedback in a styled tooltip.
Custom Validation Form
Custom javascript form validation library.