Validation

Bootstrap Validation

Note: This documentation is for an older version of Bootstrap (v.4). A newer version is available for Bootstrap 5. We recommend migrating to the latest version of our product - Material Design for Bootstrap 5.
Go to docs v.5

Provide valuable, actionable feedback to your users with HTML5 form validation – available in all our supported browsers. Choose from the browser default validation feedback, or implement custom messages with our built-in classes and starter JavaScript.

Note: For advanced users we recommend using custom validation described in this tutorial because styles as native browser defaults are not announced to screen readers.

How it works

Here’s how form validation works with Bootstrap:

  • HTML form validation is applied via CSS’s two pseudo-classes, :invalid and :valid. It applies to <input>, <select>, and <textarea> elements.
  • Bootstrap scopes the :invalid and :valid styles to their parent .was-validated class, usually applied to the <form>. Otherwise, any required field without a value shows up as invalid when a page is loaded. This way, you may choose when to activate them (typically after the form submission is attempted).
  • To reset the appearance of the form (for instance, in the case of dynamic form submissions using AJAX), remove the .was-validated class from the <form> again after submission.
  • As a fallback, .is-invalid and .is-valid classes may be used instead of the pseudo-classes for server-side validation. They do not require a .was-validated parent class.
  • Due to constraints in how CSS works, we cannot (at present) apply styles to a <label> that comes before a form control in the DOM without the use of custom JavaScript.
  • All modern browsers support the constraint validation API, a series of JavaScript methods for validating form controls.
  • Feedback messages may utilize the browser defaults (different for each browser, and unstylable via CSS) or our custom feedback styles with additional HTML and CSS.
  • You may provide custom validity messages with setCustomValidity() in JavaScript.

With that in mind, examine the following demos for our custom form validation styles, optional server-side classes, and browser defaults.

Custom styles

For custom Bootstrap form validation messages, you’ll need to add the novalidate boolean attribute to your <form>. This disables the browser default feedback tooltips, but still provides access to the form validation APIs in JavaScript. Try to submit the form below; our JavaScript will intercept the submit button and relay feedback to you.

When attempting to submit, you’ll see the :invalid and :valid styles applied to your form controls.

Default styles

Looks good!
Looks good!
@
Please choose a username.
Please provide a valid city.
Please provide a valid state.
Please provide a valid zip.
You must agree before submitting.
Edit in sandbox 
<form class="needs-validation" novalidate>
  <div class="form-row">
    <div class="col-md-4 mb-3">
      <label for="validationCustom01">First name</label>
      <input type="text" class="form-control" id="validationCustom01" placeholder="First name" value="Mark"
        required>
      <div class="valid-feedback">
        Looks good!
      </div>
    </div>
    <div class="col-md-4 mb-3">
      <label for="validationCustom02">Last name</label>
      <input type="text" class="form-control" id="validationCustom02" placeholder="Last name" value="Otto"
        required>
      <div class="valid-feedback">
        Looks good!
      </div>
    </div>
    <div class="col-md-4 mb-3">
      <label for="validationCustomUsername">Username</label>
      <div class="input-group">
        <div class="input-group-prepend">
          <span class="input-group-text" id="inputGroupPrepend">@</span>
        </div>
        <input type="text" class="form-control" id="validationCustomUsername" placeholder="Username"
          aria-describedby="inputGroupPrepend" required>
        <div class="invalid-feedback">
          Please choose a username.
        </div>
      </div>
    </div>
  </div>
  <div class="form-row">
    <div class="col-md-6 mb-3">
      <label for="validationCustom03">City</label>
      <input type="text" class="form-control" id="validationCustom03" placeholder="City" required>
      <div class="invalid-feedback">
        Please provide a valid city.
      </div>
    </div>
    <div class="col-md-3 mb-3">
      <label for="validationCustom04">State</label>
      <input type="text" class="form-control" id="validationCustom04" placeholder="State" required>
      <div class="invalid-feedback">
        Please provide a valid state.
      </div>
    </div>
    <div class="col-md-3 mb-3">
      <label for="validationCustom05">Zip</label>
      <input type="text" class="form-control" id="validationCustom05" placeholder="Zip" required>
      <div class="invalid-feedback">
        Please provide a valid zip.
      </div>
    </div>
  </div>
  <div class="form-group">
    <div class="form-check">
      <input class="form-check-input" type="checkbox" value="" id="invalidCheck" required>
      <label class="form-check-label" for="invalidCheck">
        Agree to terms and conditions
      </label>
      <div class="invalid-feedback">
        You must agree before submitting.
      </div>
    </div>
  </div>
  <button class="btn btn-primary btn-sm" type="submit">Submit form</button>
</form>
(function () {
    'use strict';
    window.addEventListener('load', function () {
      // Fetch all the forms we want to apply custom Bootstrap validation styles to
      var forms = document.getElementsByClassName('needs-validation');
      // Loop over them and prevent submission
      var validation = Array.prototype.filter.call(forms, function (form) {
        form.addEventListener('submit', function (event) {
          if (form.checkValidity() === false) {
            event.preventDefault();
            event.stopPropagation();
          }
          form.classList.add('was-validated');
        }, false);
      });
    }, false);
  })();

Material styles MDB Pro component

Looks good!
Looks good!
Please choose a username.
Please provide a valid city.
Please provide a valid state.
Please provide a valid zip.
You must agree before submitting.
Edit in sandbox 
<form class="needs-validation" novalidate>
  <div class="form-row">
    <div class="col-md-4 mb-3 md-form">
      <label for="validationCustom012">First name</label>
      <input type="text" class="form-control" id="validationCustom012" placeholder="First name" value="Mark"
        required>
      <div class="valid-feedback">
        Looks good!
      </div>
    </div>
    <div class="col-md-4 mb-3 md-form">
      <label for="validationCustom022">Last name</label>
      <input type="text" class="form-control" id="validationCustom022" value="Otto" required>
      <div class="valid-feedback">
        Looks good!
      </div>
    </div>
    <div class="col-md-4 mb-3 md-form">
      <label for="validationCustomUsername2">Username</label>
      <input type="text" class="form-control" id="validationCustomUsername2" aria-describedby="inputGroupPrepend2"
        required>
      <div class="invalid-feedback">
        Please choose a username.
      </div>
    </div>
  </div>
  <div class="form-row">
    <div class="col-md-6 mb-3 md-form">
      <label for="validationCustom032">City</label>
      <input type="text" class="form-control" id="validationCustom032" required>
      <div class="invalid-feedback">
        Please provide a valid city.
      </div>
    </div>
    <div class="col-md-3 mb-3 md-form">
      <label for="validationCustom042">State</label>
      <input type="text" class="form-control" id="validationCustom042" required>
      <div class="invalid-feedback">
        Please provide a valid state.
      </div>
    </div>
    <div class="col-md-3 mb-3 md-form">
      <label for="validationCustom052">Zip</label>
      <input type="text" class="form-control" id="validationCustom052" required>
      <div class="invalid-feedback">
        Please provide a valid zip.
      </div>
    </div>
  </div>
  <div class="form-group">
    <div class="form-check pl-0">
      <input class="form-check-input" type="checkbox" value="" id="invalidCheck2" required>
      <label class="form-check-label" for="invalidCheck2">
        Agree to terms and conditions
      </label>
      <div class="invalid-feedback">
        You must agree before submitting.
      </div>
    </div>
  </div>
  <button class="btn btn-primary btn-sm btn-rounded" type="submit">Submit form</button>
</form>
(function () {
    'use strict';
    window.addEventListener('load', function () {
      // Fetch all the forms we want to apply custom Bootstrap validation styles to
      var forms = document.getElementsByClassName('needs-validation');
      // Loop over them and prevent submission
      var validation = Array.prototype.filter.call(forms, function (form) {
        form.addEventListener('submit', function (event) {
          if (form.checkValidity() === false) {
            event.preventDefault();
            event.stopPropagation();
          }
          form.classList.add('was-validated');
        }, false);
      });
    }, false);
  })();

Browser defaults

Not interested in custom validation feedback messages or writing JavaScript to change form behaviors? That's fine, you can use the browser defaults. Try submitting the form below. Depending on your browser and OS, you’ll see a slightly different style of feedback.

While these feedback styles cannot be styled with CSS, you can still customize the feedback text through JavaScript.

Default styles

@
Edit in sandbox 
<form>
  <div class="form-row">
    <div class="col-md-4 mb-3">
      <label for="validationDefault01">First name</label>
      <input type="text" class="form-control" id="validationDefault01" placeholder="First name" value="Mark"
        required>
    </div>
    <div class="col-md-4 mb-3">
      <label for="validationDefault02">Last name</label>
      <input type="text" class="form-control" id="validationDefault02" placeholder="Last name" value="Otto"
        required>
    </div>
    <div class="col-md-4 mb-3">
      <label for="validationDefaultUsername">Username</label>
      <div class="input-group">
        <div class="input-group-prepend">
          <span class="input-group-text" id="inputGroupPrepend21">@</span>
        </div>
        <input type="text" class="form-control" id="validationDefaultUsername" placeholder="Username"
          aria-describedby="inputGroupPrepend21" required>
      </div>
    </div>
  </div>
  <div class="form-row">
    <div class="col-md-6 mb-3">
      <label for="validationDefault03">City</label>
      <input type="text" class="form-control" id="validationDefault03" placeholder="City" required>
    </div>
    <div class="col-md-3 mb-3">
      <label for="validationDefault04">State</label>
      <input type="text" class="form-control" id="validationDefault04" placeholder="State" required>
    </div>
    <div class="col-md-3 mb-3">
      <label for="validationDefault05">Zip</label>
      <input type="text" class="form-control" id="validationDefault05" placeholder="Zip" required>
    </div>
  </div>
  <div class="form-group">
    <div class="custom-control custom-checkbox">
      <input type="checkbox" class="custom-control-input" id="invalidCheck12" required>
      <label class="custom-control-label" for="invalidCheck">Agree to terms and conditions</label>
    </div>
  </div>
  <button class="btn btn-primary btn-sm" type="submit">Submit form</button>
</form>

Material stylesMDB Pro component

Edit in sandbox 
<form>
  <div class="form-row">
    <div class="col-md-4 mb-3 md-form">
      <label for="validationDefault22">First name</label>
      <input type="text" class="form-control" id="validationDefault22" value="Mark" required>
    </div>
    <div class="col-md-4 mb-3 md-form">
      <label for="validationDefault22">Last name</label>
      <input type="text" class="form-control" id="validationDefault22" value="Otto" required>
    </div>
    <div class="col-md-4 mb-3 md-form">
      <label for="validationDefaultUsername22">Username</label>
      <input type="text" class="form-control" id="validationDefaultUsername22" aria-describedby="inputGroupPrepend23"
        required>
    </div>
  </div>
  <div class="form-row">
    <div class="col-md-6 mb-3 md-form">
      <label for="validationDefault22">City</label>
      <input type="text" class="form-control" id="validationDefault22" required>
    </div>
    <div class="col-md-3 mb-3 md-form">
      <label for="validationDefault22">State</label>
      <input type="text" class="form-control" id="validationDefault22" required>
    </div>
    <div class="col-md-3 mb-3 md-form">
      <label for="validationDefault22">Zip</label>
      <input type="text" class="form-control" id="validationDefault22" required>
    </div>
  </div>
  <div class="form-group">
    <div class="form-check pl-0">
      <input class="form-check-input" type="checkbox" value="" id="invalidCheck222" required>
      <label class="form-check-label" for="invalidCheck222">
        Agree to terms and conditions
      </label>
    </div>
  </div>
  <button class="btn btn-primary btn-sm" type="submit">Submit form</button>
</form>

Server side

We recommend using client-side validation, but in case you require server side, you can indicate invalid and valid form fields with .is-invalid and .is-valid. Note that .invalid-feedback is also supported by these classes.

Default styles

Looks good!
Looks good!
@
Please choose a username.
Please provide a valid city.
Please provide a valid state.
Please provide a valid zip.
You must agree before submitting.
You must agree before submitting.
Edit in sandbox 
<form>
  <div class="form-row">
    <div class="col-md-4 mb-3">
      <label for="validationServer013">First name</label>
      <input type="text" class="form-control is-valid" id="validationServer013" placeholder="First name"
        value="Mark" required>
      <div class="valid-feedback">
        Looks good!
      </div>
    </div>
    <div class="col-md-4 mb-3">
      <label for="validationServer023">Last name</label>
      <input type="text" class="form-control is-valid" id="validationServer023" placeholder="Last name"
        value="Otto" required>
      <div class="valid-feedback">
        Looks good!
      </div>
    </div>
    <div class="col-md-4 mb-3">
      <label for="validationServerUsername33">Username</label>
      <div class="input-group">
        <div class="input-group-prepend">
          <span class="input-group-text" id="inputGroupPrepend33">@</span>
        </div>
        <input type="text" class="form-control is-invalid" id="validationServerUsername33" placeholder="Username"
          aria-describedby="inputGroupPrepend33" required>
        <div class="invalid-feedback">
          Please choose a username.
        </div>
      </div>
    </div>
  </div>
  <div class="form-row">
    <div class="col-md-6 mb-3">
      <label for="validationServer033">City</label>
      <input type="text" class="form-control is-invalid" id="validationServer033" placeholder="City"
        required>
      <div class="invalid-feedback">
        Please provide a valid city.
      </div>
    </div>
    <div class="col-md-3 mb-3">
      <label for="validationServer043">State</label>
      <input type="text" class="form-control is-invalid" id="validationServer043" placeholder="State"
        required>
      <div class="invalid-feedback">
        Please provide a valid state.
      </div>
    </div>
    <div class="col-md-3 mb-3">
      <label for="validationServer053">Zip</label>
      <input type="text" class="form-control is-invalid" id="validationServer053" placeholder="Zip"
        required>
      <div class="invalid-feedback">
        Please provide a valid zip.
      </div>
    </div>
  </div>
  <div class="form-group">
    <div class="custom-control custom-checkbox">
      <input type="checkbox" class="custom-control-input is-invalid" id="invalidCheck33" required>
      <label class="custom-control-label" for="invalidCheck33">Agree to terms and conditions</label>
      <div class="invalid-feedback">
        You must agree before submitting.
      </div>
    </div>
    <div class="invalid-feedback">
      You must agree before submitting.
    </div>
  </div>
  <button class="btn btn-primary btn-sm" type="submit">Submit form</button>
</form>

Material styles

Looks good!
Looks good!
Please choose a username.
Please provide a valid city.
Please provide a valid state.
Please provide a valid zip.
You must agree before submitting.
Edit in sandbox 
<form>
  <div class="form-row">
    <div class="col-md-4 mb-3 md-form">
      <label for="validationServer015">First name</label>
      <input type="text" class="form-control is-valid" id="validationServer015" value="Mark" required>
      <div class="valid-feedback">
        Looks good!
      </div>
    </div>
    <div class="col-md-4 mb-3 md-form">
      <label for="validationServer025">Last name</label>
      <input type="text" class="form-control is-valid" id="validationServer025" value="Otto" required>
      <div class="valid-feedback">
        Looks good!
      </div>
    </div>
    <div class="col-md-4 mb-3 md-form">
      <label for="validationServerUsername55">Username</label>
      <input type="text" class="form-control is-invalid" id="validationServerUsername55" required>
      <div class="invalid-feedback">
        Please choose a username.
      </div>
    </div>
  </div>
  <div class="form-row">
    <div class="col-md-6 mb-3 md-form">
      <label for="validationServer035">City</label>
      <input type="text" class="form-control is-invalid" id="validationServer035" required>
      <div class="invalid-feedback">
        Please provide a valid city.
      </div>
    </div>
    <div class="col-md-3 mb-3 md-form">
      <label for="validationServer045">State</label>
      <input type="text" class="form-control is-invalid" id="validationServer045" required>
      <div class="invalid-feedback">
        Please provide a valid state.
      </div>
    </div>
    <div class="col-md-3 mb-3 md-form">
      <label for="validationServer055">Zip</label>
      <input type="text" class="form-control is-invalid" id="validationServer055" required>
      <div class="invalid-feedback">
        Please provide a valid zip.
      </div>
    </div>
  </div>
  <div class="form-group">
    <div class="form-check pl-0 md-form m-0">
      <input class="form-check-input is-invalid" type="checkbox" value="" id="invalidCheck35" required>
      <label class="form-check-label" for="invalidCheck35">
        Agree to terms and conditions
      </label>
    </div>
    <div class="invalid-feedback mt-3 ml-4">
      You must agree before submitting.
    </div>
  </div>
  <button class="btn btn-primary btn-sm btn-rounded" type="submit">Submit form</button>
</form>

Supported elements

Our example forms show native textual <input>s above, but form validation styles are available for our custom form controls, as well.

Default styles

Example invalid feedback text
More example invalid feedback text
Example invalid custom select feedback
Example invalid custom file feedback
Edit in sandbox 
<form class="was-validated">
  <div class="custom-control custom-checkbox mb-3">
    <input type="checkbox" class="custom-control-input" id="customControlValidation1" required>
    <label class="custom-control-label" for="customControlValidation1">Check this custom checkbox</label>
    <div class="invalid-feedback">Example invalid feedback text</div>
  </div>

  <div class="custom-control custom-radio">
    <input type="radio" class="custom-control-input" id="customControlValidation2" name="radio-stacked"
      required>
    <label class="custom-control-label" for="customControlValidation2">Toggle this custom radio</label>
  </div>
  <div class="custom-control custom-radio mb-3">
    <input type="radio" class="custom-control-input" id="customControlValidation3" name="radio-stacked"
      required>
    <label class="custom-control-label" for="customControlValidation3">Or toggle this other custom radio</label>
    <div class="invalid-feedback">More example invalid feedback text</div>
  </div>

  <div class="form-group">
    <select class="custom-select browser-default" required>
      <option value="">Open this select menu</option>
      <option value="1">One</option>
      <option value="2">Two</option>
      <option value="3">Three</option>
    </select>
    <div class="invalid-feedback">Example invalid custom select feedback</div>
  </div>

  <div class="custom-file">
    <input type="file" class="custom-file-input" id="validatedCustomFile" required>
    <label class="custom-file-label" for="validatedCustomFile">Choose file...</label>
    <div class="invalid-feedback">Example invalid custom file feedback</div>
  </div>
</form>

Material styles MDB Pro component

Example invalid feedback text
More example invalid feedback text
Choose file
Example invalid custom file feedback
Edit in sandbox 
<form class="was-validated">
  <div class="custom-control custom-checkbox mb-3">
    <input type="checkbox" class="custom-control-input" id="customControlValidation1" required>
    <label class="custom-control-label" for="customControlValidation1">Check this custom checkbox</label>
    <div class="invalid-feedback">Example invalid feedback text</div>
  </div>

  <div class="custom-control custom-radio">
    <input type="radio" class="custom-control-input" id="customControlValidation2" name="radio-stacked"
      required>
    <label class="custom-control-label" for="customControlValidation2">Toggle this custom radio</label>
  </div>
  <div class="custom-control custom-radio mb-3">
    <input type="radio" class="custom-control-input" id="customControlValidation3" name="radio-stacked"
      required>
    <label class="custom-control-label" for="customControlValidation3">Or toggle this other custom radio</label>
    <div class="invalid-feedback">More example invalid feedback text</div>
  </div>

  <div class="form-group">
    <select class="custom-select browser-default" required>
      <option value="">Open this select menu</option>
      <option value="1">One</option>
      <option value="2">Two</option>
      <option value="3">Three</option>
    </select>
    <div class="invalid-feedback">Example invalid custom select feedback</div>
  </div>

  <div class="custom-file">
    <input type="file" class="custom-file-input" id="validatedCustomFile" required>
    <label class="custom-file-label" for="validatedCustomFile">Choose file...</label>
    <div class="invalid-feedback">Example invalid custom file feedback</div>
  </div>
</form>

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. Be sure to have a parent with position: relative to it for tooltip positioning. In the example below, our column classes have this already, but your project may require an alternative setup.

Default styles

Looks good!
Looks good!
@
Please choose a unique and valid username.
Please provide a valid city.
Please provide a valid state.
Please provide a valid zip.
Edit in sandbox 
<form class="needs-validation" novalidate>
  <div class="form-row">
    <div class="col-md-4 mb-3">
      <label for="validationTooltip01">First name</label>
      <input type="text" class="form-control" id="validationTooltip01" placeholder="First name" value="Mark"
        required>
      <div class="valid-tooltip">
        Looks good!
      </div>
    </div>
    <div class="col-md-4 mb-3">
      <label for="validationTooltip02">Last name</label>
      <input type="text" class="form-control" id="validationTooltip02" placeholder="Last name" value="Otto"
        required>
      <div class="valid-tooltip">
        Looks good!
      </div>
    </div>
    <div class="col-md-4 mb-3">
      <label for="validationTooltipUsername">Username</label>
      <div class="input-group">
        <div class="input-group-prepend">
          <span class="input-group-text" id="validationTooltipUsernamePrepend">@</span>
        </div>
        <input type="text" class="form-control" id="validationTooltipUsername" placeholder="Username"
          aria-describedby="validationTooltipUsernamePrepend" required>
        <div class="invalid-tooltip">
          Please choose a unique and valid username.
        </div>
      </div>
    </div>
  </div>
  <div class="form-row">
    <div class="col-md-6 mb-3">
      <label for="validationTooltip03">City</label>
      <input type="text" class="form-control" id="validationTooltip03" placeholder="City" required>
      <div class="invalid-tooltip">
        Please provide a valid city.
      </div>
    </div>
    <div class="col-md-3 mb-3">
      <label for="validationTooltip04">State</label>
      <input type="text" class="form-control" id="validationTooltip04" placeholder="State" required>
      <div class="invalid-tooltip">
        Please provide a valid state.
      </div>
    </div>
    <div class="col-md-3 mb-3">
      <label for="validationTooltip05">Zip</label>
      <input type="text" class="form-control" id="validationTooltip05" placeholder="Zip" required>
      <div class="invalid-tooltip">
        Please provide a valid zip.
      </div>
    </div>
  </div>
  <button class="btn btn-primary btn-sm" type="submit">Submit form</button>
</form>
// Tooltips Initialization
$(function () {
  $('[data-toggle="tooltip"]').tooltip()
})

Material styles MDB Pro component

Looks good!
Looks good!
Please choose a unique and valid username.>
Please provide a valid city.
Please provide a valid state.
Please provide a valid zip.
Edit in sandbox 
<form class="needs-validation" novalidate>
  <div class="form-row">
    <div class="col-md-4 mb-3 md-form">
      <label for="validationTooltip011">First name</label>
      <input type="text" class="form-control" id="validationTooltip011" value="Mark" required>
      <div class="valid-tooltip">
        Looks good!
      </div>
    </div>
    <div class="col-md-4 mb-3 md-form">
      <label for="validationTooltip021">Last name</label>
      <input type="text" class="form-control" id="validationTooltip021" value="Otto" required>
      <div class="valid-tooltip">
        Looks good!
      </div>
    </div>
    <div class="col-md-4 mb-3 md-form">
      <label for="validationTooltipUsername1">Username</label>
      <input type="text" class="form-control" id="validationTooltipUsername1" required>
      <div class="invalid-tooltip">
        Please choose a unique and valid username.>
      </div>
    </div>
  </div>
  <div class="form-row">
    <div class="col-md-6 mb-3 md-form">
      <label for="validationTooltip031">City</label>
      <input type="text" class="form-control" id="validationTooltip031" required>
      <div class="invalid-tooltip">
        Please provide a valid city.
      </div>
    </div>
    <div class="col-md-3 mb-3 md-form">
      <label for="validationTooltip041">State</label>
      <input type="text" class="form-control" id="validationTooltip041" required>
      <div class="invalid-tooltip">
        Please provide a valid state.
      </div>
    </div>
    <div class="col-md-3 mb-3 md-form">
      <label for="validationTooltip051">Zip</label>
      <input type="text" class="form-control" id="validationTooltip051" required>
      <div class="invalid-tooltip">
        Please provide a valid zip.
      </div>
    </div>
  </div>
  <button class="btn btn-primary btn-sm btn-rounded" type="submit">Submit form</button>
</form>
// Tooltips Initialization
$(function () {
  $('[data-toggle="tooltip"]').tooltip()
})

DatePicker Validation MDB Pro component"

Please select a valid date.
You shall not pass!
Edit in sandbox 
<form class="needs-validation container" novalidate>
  <div class="mb-3 md-form">
    <input type="text" name="date" id="date" class="form-control datepicker" value="" required />
    <label for="date">Date</label>
    <div class="invalid-feedback">Please select a valid date.</div>
  </div>

  <div class="form-row my-4">
    <div class="form-check pl-0">
      <input class="form-check-input" type="checkbox" value="" id="invalidCheck266" required>
      <label class="form-check-label" for="invalidCheck266">Agree to terms and conditions</label>
      <div class="invalid-feedback">You shall not pass!</div>
    </div>
  </div>
  <button class="btn btn-primary btn-sm btn-rounded" type="submit">Submit form</button>
</form>
(function () {
    'use strict';
    window.addEventListener('load', function () {
      // Fetch all the forms we want to apply custom Bootstrap validation styles to
      var forms = document.getElementsByClassName('needs-validation');
      // Loop over them and prevent submission
      var validation = Array.prototype.filter.call(forms, function (form) {
        form.addEventListener('submit', function (event) {
          if (form.checkValidity() === false) {
            event.preventDefault();
            event.stopPropagation();
          }
          form.classList.add('was-validated');
        }, false);
      });
    }, false);
  })();

  $(document).ready(function () {
    $('.datepicker').pickadate();
    $('.datepicker').removeAttr('readonly');
  });

Material Select Validation MDB Pro component"

▼
Please select a country.
You shall not pass!
Edit in sandbox 
<form class="needs-validation container" novalidate>
  <div class="form-row">
    <div class="mb-3 md-form">
      <select class="mdb-select" required>
        <option value="1">USA</option>
        <option value="2">Germany</option>
        <option value="3">Poland</option>
      </select>
      <div class="invalid-feedback">Please select a country.</div>
    </div>
  </div>
  <div class="form-row mb-4">
    <div class="form-check pl-0">
      <input class="form-check-input" type="checkbox" value="" id="invalidCheck29" required>
      <label class="form-check-label" for="invalidCheck29">Agree to terms and conditions</label>
      <div class="invalid-feedback">You shall not pass!</div>
    </div>
  </div>
  <button class="btn btn-primary btn-sm btn-rounded" type="submit">Submit form</button>
</form>
(function () {
    'use strict';
    window.addEventListener('load', function () {
      // Fetch all the forms we want to apply custom Bootstrap validation styles to
      var forms = document.getElementsByClassName('needs-validation');
      // Loop over them and prevent submission
      var validation = Array.prototype.filter.call(forms, function (form) {
        form.addEventListener('submit', function (event) {
          if (form.checkValidity() === false) {
            event.preventDefault();
            event.stopPropagation();
          }
          form.classList.add('was-validated');
        }, false);
      });
    }, false);
  })();

  $(document).ready(function () {
    $('.mdb-select').materialSelect();
    $('.mdb-select.select-wrapper .select-dropdown').val("").removeAttr('readonly').attr("placeholder",
      "Choose your country ").prop('required', true).addClass('form-control').css('background-color', '#fff');
  });