Bootstrap 5 Form Validation
You can use different validation classes to provide valuable feedback to users. Add either .was-validated or .needs-validation to the <form> element, depending on whether you want to provide validation feedback before or after submitting the form. The input fields will have a green (valid) or red (invalid) border to indicate what's missing in the form. You can also add a .valid-feedback or .invalid-feedback message to tell the user explicitly what's missing, or needs to be done before submitting the form.
Example
<form action="/action_page.php" class="was-validated">
<div class="mb-3 mt-3">
<label for="uname" class="form-label">Username:<
<input type="text" class="form-control" id="uname" placeholder="Enter username" name="uname" required>
<div class="valid-feedback">Valid.</div>
<div class="invalid-feedback">Please fill out this field.</div>
</div>
<div class="mb-3">
<label for="pwd" class="form-label">Password:</label>
<
<div class="valid-feedback">Valid.</div>
<div class="invalid-feedback">Please fill out this field.</div>
</div>
<div class="form-check mb-3">
<input class="form-check-input" type="checkbox" id="myCheck" name="remember" required>
<label class="form-check-label" for="myCheck">I agree on blabla.</label>
<div class="valid-feedback">Valid.</div>
<div class="invalid-feedback">Check this checkbox to continue.</div>
</div>
<button type="submit" class="btn btn-primary">Submit</button>
</form>
You can click on above box to edit the code and run again.