Examples and usage guidelines for form control styles, layout options, and custom components for creating a wide variety of forms.
Overview
Bootstrap’s form controls expand on
our Rebooted form styles
with classes. Use these classes to opt into their customized displays for a more consistent rendering across browsers and devices.
Be sure to use an appropriate
type
attribute on all inputs (e.g.,
email
for email address or
number
for numerical information) to take advantage of newer input controls like email verification, number selection, and more.
Here’s a quick example to demonstrate Bootstrap’s form styles. Keep reading for documentation on required classes, form layout, and more.
Textual form controls—like
<input>
s,
<select>
s, and
<textarea>
s—are styled with the
.form-control
class. Included are styles for general appearance, focus state, sizing, and more.
Be sure to explore our
custom forms
to further style
<select>
s.
Add the
readonly
boolean attribute on an input to prevent modification of the input’s value. Read-only inputs appear lighter (just like disabled inputs), but retain the standard cursor.
If you want to have
<input readonly>
elements in your form styled as plain text, use the
.form-control-plaintext
class to remove the default form field styling and preserve the correct margin and padding.
Default checkboxes and radios are improved upon with the help of
.form-check
,
a single class for both input types that improves the layout and behavior of their HTML elements
. Checkboxes are for selecting one or several options in a list, while radios are for selecting one option from many.
Disabled checkboxes and radios are supported, but to provide a
not-allowed
cursor on hover of the parent
<label>
, you’ll need to add the
disabled
attribute to the
.form-check-input
. The disabled attribute will apply a lighter color to help indicate the input’s state.
Checkboxes and radios use are built to support HTML-based form validation and provide concise, accessible labels. As such, our
<input>
s and
<label>
s are sibling elements as opposed to an
<input>
within a
<label>
. This is slightly more verbose as you must specify
id
and
for
attributes to relate the
<input>
and
<label>
.
Default (stacked)
By default, any number of checkboxes and radios that are immediate sibling will be vertically stacked and appropriately spaced with
.form-check
.
<divclass="form-check"><inputclass="form-check-input"type="radio"name="exampleRadios"id="exampleRadios1"value="option1"checked><labelclass="form-check-label"for="exampleRadios1">
Default radio
</label><divclass="form-check"><inputclass="form-check-input"type="radio"name="exampleRadios"id="exampleRadios2"value="option2"><labelclass="form-check-label"for="exampleRadios2">
Second default radio
</label><divclass="form-check"><inputclass="form-check-input"type="radio"name="exampleRadios"id="exampleRadios3"value="option3"disabled><labelclass="form-check-label"for="exampleRadios3">
Disabled radio
</label>
Inline
Group checkboxes or radios on the same horizontal row by adding .form-check-inline to any .form-check.
Add .position-static to inputs within .form-check that don’t have any label text. Remember to still provide some form of label for assistive technologies (for instance, using aria-label).
Since Bootstrap applies display: block and width: 100% to almost all our form controls, forms will by default stack vertically. Additional classes can be used to vary this layout on a per-form basis.
Form groups
The .form-group class is the easiest way to add some structure to forms. It provides a flexible class that encourages proper grouping of labels, controls, optional help text, and form validation messaging. By default it only applies margin-bottom, but it picks up additional styles in .form-inline as needed. Use it with <fieldset>s, <div>s, or nearly any other element.
More complex forms can be built using our grid classes. Use these for form layouts that require multiple columns, varied widths, and additional alignment options.
You may also swap .row for .form-row, a variation of our standard grid row that overrides the default column gutters for tighter and more compact layouts.
More complex layouts can also be created with the grid system.
<divclass="form-row"><divclass="form-group col-md-6"><labelfor="inputEmail4">Email</label><inputtype="email"class="form-control"id="inputEmail4"placeholder="Email"><divclass="form-group col-md-6"><labelfor="inputPassword4">Password</label><inputtype="password"class="form-control"id="inputPassword4"placeholder="Password"><divclass="form-group"><labelfor="inputAddress">Address</label><inputtype="text"class="form-control"id="inputAddress"placeholder="1234 Main St"><divclass="form-group"><labelfor="inputAddress2">Address 2</label><inputtype="text"class="form-control"id="inputAddress2"placeholder="Apartment, studio, or floor"><divclass="form-row"><divclass="form-group col-md-6"><labelfor="inputCity">City</label><inputtype="text"class="form-control"id="inputCity"><divclass="form-group col-md-4"><labelfor="inputState">State</label><selectid="inputState"class="form-control"><optionselected>Choose...</option><option>...</option></select><divclass="form-group col-md-2"><labelfor="inputZip">Zip</label><inputtype="text"class="form-control"id="inputZip"><divclass="form-group"><divclass="form-check"><inputclass="form-check-input"type="checkbox"id="gridCheck"><labelclass="form-check-label"for="gridCheck">
Check me out
</label><buttontype="submit"class="btn btn-primary">Sign in</button></form>
Horizontal form
Create horizontal forms with the grid by adding the .row class to form groups and using the .col-*-* classes to specify the width of your labels and controls. Be sure to add .col-form-label to your <label>s as well so they’re vertically centered with their associated form controls.
At times, you maybe need to use margin or padding utilities to create that perfect alignment you need. For example, we’ve removed the padding-top on our stacked radio inputs label to better align the text baseline.
<divclass="form-group row"><labelfor="inputEmail3"class="col-sm-2 col-form-label">Email</label><divclass="col-sm-10"><inputtype="email"class="form-control"id="inputEmail3"placeholder="Email"><divclass="form-group row"><labelfor="inputPassword3"class="col-sm-2 col-form-label">Password</label><divclass="col-sm-10"><inputtype="password"class="form-control"id="inputPassword3"placeholder="Password"><fieldsetclass="form-group"><divclass="row"><legendclass="col-form-label col-sm-2 pt-0">Radios</legend><divclass="col-sm-10"><divclass="form-check"><inputclass="form-check-input"type="radio"name="gridRadios"id="gridRadios1"value="option1"checked><labelclass="form-check-label"for="gridRadios1">
First radio
</label><divclass="form-check"><inputclass="form-check-input"type="radio"name="gridRadios"id="gridRadios2"value="option2"><labelclass="form-check-label"for="gridRadios2">
Second radio
</label><divclass="form-check disabled"><inputclass="form-check-input"type="radio"name="gridRadios"id="gridRadios3"value="option3"disabled><labelclass="form-check-label"for="gridRadios3">
Third disabled radio
</label></fieldset><divclass="form-group row"><divclass="col-sm-2">Checkbox</div><divclass="col-sm-10"><divclass="form-check"><inputclass="form-check-input"type="checkbox"id="gridCheck1"><labelclass="form-check-label"for="gridCheck1">
Example checkbox
</label><divclass="form-group row"><divclass="col-sm-10"><buttontype="submit"class="btn btn-primary">Sign in</button></form>
Horizontal form label sizing
Be sure to use
.col-form-label-sm
or
.col-form-label-lg
to your
<label>
s or
<legend>
s to correctly follow the size of
.form-control-lg
and
.form-control-sm
.
As shown in the previous examples, our grid system allows you to place any number of
.col
s within a
.row
or
.form-row
. They’ll split the available width equally between them. You may also pick a subset of your columns to take up more or less space, while the remaining
.col
s equally split the rest, with specific column classes like
.col-7
.
The example below uses a flexbox utility to vertically center the contents and changes
.col
to
.col-auto
so that your columns only take up as much space as needed. Put another way, the column sizes itself based on the contents.
Use the
.form-inline
class to display a series of labels, form controls, and buttons on a single horizontal row. Form controls within inline forms vary slightly from their default states.
Controls are
display: flex
, collapsing any HTML white space and allowing you to provide alignment control with
spacing
and
flexbox
utilities.
Controls and input groups receive
width: auto
to override the Bootstrap default
width: 100%
.
Controls
only appear inline in viewports that are at least 576px wide
to account for narrow viewports on mobile devices.
You may need to manually address the width and alignment of individual form controls with
spacing utilities
(as shown below). Lastly, be sure to always include a
<label>
with each form control, even if you need to hide it from non-screenreader visitors with
.sr-only
.
Assistive technologies such as screen readers will have trouble with your forms if you don’t include a label for every input. For these inline forms, you can hide the labels using the
.sr-only
class. There are further alternative methods of providing a label for assistive technologies, such as the
aria-label
,
aria-labelledby
or
title
attribute. If none of these are present, assistive technologies may resort to using the
placeholder
attribute, if present, but note that use of
placeholder
as a replacement for other labelling methods is not advised.
Help text
Block-level help text in forms can be created using
.form-text
(previously known as
.help-block
in v3). Inline help text can be flexibly implemented using any inline HTML element and utility classes like
.text-muted
.
Associating help text with form controls
Help text should be explicitly associated with the form control it relates to using the
aria-describedby
attribute. This will ensure that assistive technologies—such as screen readers—will announce this help text when the user focuses or enters the control.
Help text below inputs can be styled with
.form-text
. This class includes
display: block
and adds some top margin for easy spacing from the inputs above.
Your password must be 8-20 characters long, contain letters and numbers, and must not contain spaces, special characters, or emoji.
<labelfor="inputPassword5">Password</label><inputtype="password"id="inputPassword5"class="form-control"aria-describedby="passwordHelpBlock"><smallid="passwordHelpBlock"class="form-text text-muted">
Your password must be 8-20 characters long, contain letters and numbers, and must not contain spaces, special characters, or emoji.
</small>
Inline text can use any typical inline HTML element (be it a
<small>
,
<span>
, or something else) with nothing more than a utility class.
<formclass="form-inline"><divclass="form-group"><labelfor="inputPassword6">Password</label><inputtype="password"id="inputPassword6"class="form-control mx-sm-3"aria-describedby="passwordHelpInline"><smallid="passwordHelpInline"class="text-muted">
Must be 8-20 characters long.
</small></form>
Disabled forms
Add the
disabled
boolean attribute on an input to prevent user interactions and make it appear lighter.
By default, browsers will treat all native form controls (
<input>
,
<select>
and
<button>
elements) inside a
<fieldset disabled>
as disabled, preventing both keyboard and mouse interactions on them. However, if your form also includes
<a ... class="btn btn-*">
elements, these will only be given a style of
pointer-events: none
. As noted in the section about
disabled state for buttons
(and specifically in the sub-section for anchor elements), this CSS property is not yet standardized and isn’t fully supported in Internet Explorer 10, and won’t prevent keyboard users from being able to focus or activate these links. So to be safe, use custom JavaScript to disable such links.
Cross-browser compatibility
While Bootstrap will apply these styles in all browsers, Internet Explorer 11 and below don’t fully support the
disabled
attribute on a
<fieldset>
. Use custom JavaScript to disable the fieldset in these browsers.
Validation
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.
We currently recommend using custom validation styles, as native browser default validation messages are not consistently exposed to assistive technologies in all browsers (most notably, Chrome on desktop and mobile).
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 parent
.was-validated
class, usually applied to the
<form>
. Otherwise, any required field without a value shows up as invalid on page load. This way, you may choose when to activate them (typically after 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 help 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, consider 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.
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
.custom-select
, and not
.form-control
.
<formclass="needs-validation"novalidate><divclass="form-row"><divclass="col-md-4 mb-3"><labelfor="validationCustom01">First name</label><inputtype="text"class="form-control"id="validationCustom01"placeholder="First name"value="Mark"required><divclass="valid-feedback">
Looks good!
<divclass="col-md-4 mb-3"><labelfor="validationCustom02">Last name</label><inputtype="text"class="form-control"id="validationCustom02"placeholder="Last name"value="Otto"required><divclass="valid-feedback">
Looks good!
<divclass="col-md-4 mb-3"><labelfor="validationCustomUsername">Username</label><divclass="input-group"><divclass="input-group-prepend"><spanclass="input-group-text"id="inputGroupPrepend">@</span><inputtype="text"class="form-control"id="validationCustomUsername"placeholder="Username"aria-describedby="inputGroupPrepend"required><divclass="invalid-feedback">
Please choose a username.
<divclass="form-row"><divclass="col-md-6 mb-3"><labelfor="validationCustom03">City</label><inputtype="text"class="form-control"id="validationCustom03"placeholder="City"required><divclass="invalid-feedback">
Please provide a valid city.
<divclass="col-md-3 mb-3"><labelfor="validationCustom04">State</label><inputtype="text"class="form-control"id="validationCustom04"placeholder="State"required><divclass="invalid-feedback">
Please provide a valid state.
<divclass="col-md-3 mb-3"><labelfor="validationCustom05">Zip</label><inputtype="text"class="form-control"id="validationCustom05"placeholder="Zip"required><divclass="invalid-feedback">
Please provide a valid zip.
<divclass="form-group"><divclass="form-check"><inputclass="form-check-input"type="checkbox"value=""id="invalidCheck"required><labelclass="form-check-label"for="invalidCheck">
Agree to terms and conditions
</label><divclass="invalid-feedback">
You must agree before submitting.
<buttonclass="btn btn-primary"type="submit">Submit form</button></form><script>// Example starter JavaScript for disabling form submissions if there are invalid fields(function(){'use strict';window.addEventListener('load',function(){// Fetch all the forms we want to apply custom Bootstrap validation styles tovarforms=document.getElementsByClassName('needs-validation');// Loop over them and prevent submissionvarvalidation=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);})();</script>
Browser defaults
Not interested in custom validation feedback messages or writing JavaScript to change form behaviors? All good, 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.
We recommend using client-side validation, but in case you require server-side validation, you can indicate invalid and valid form fields with
.is-invalid
and
.is-valid
. Note that
.invalid-feedback
is also supported with these classes.
Our example forms show native textual
<input>
s above, but form validation styles are also available for
<textarea>
s and custom form controls.
<formclass="was-validated"><divclass="mb-3"><labelfor="validationTextarea">Textarea</label><textareaclass="form-control is-invalid"id="validationTextarea"placeholder="Required example textarea"required></textarea><divclass="invalid-feedback">
Please enter a message in the textarea.
<divclass="custom-control custom-checkbox mb-3"><inputtype="checkbox"class="custom-control-input"id="customControlValidation1"required><labelclass="custom-control-label"for="customControlValidation1">Check this custom checkbox</label><divclass="invalid-feedback">Example invalid feedback text</div><divclass="custom-control custom-radio"><inputtype="radio"class="custom-control-input"id="customControlValidation2"name="radio-stacked"required><labelclass="custom-control-label"for="customControlValidation2">Toggle this custom radio</label><divclass="custom-control custom-radio mb-3"><inputtype="radio"class="custom-control-input"id="customControlValidation3"name="radio-stacked"required><labelclass="custom-control-label"for="customControlValidation3">Or toggle this other custom radio</label><divclass="invalid-feedback">More example invalid feedback text</div><divclass="form-group"><selectclass="custom-select"required><optionvalue="">Open this select menu</option><optionvalue="1">One</option><optionvalue="2">Two</option><optionvalue="3">Three</option></select><divclass="invalid-feedback">Example invalid custom select feedback</div><divclass="custom-file"><inputtype="file"class="custom-file-input"id="validatedCustomFile"required><labelclass="custom-file-label"for="validatedCustomFile">Choose file...</label><divclass="invalid-feedback">Example invalid custom file feedback</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
on it for tooltip positioning. In the example below, our column classes have this already, but your project may require an alternative setup.
<formclass="needs-validation"novalidate><divclass="form-row"><divclass="col-md-4 mb-3"><labelfor="validationTooltip01">First name</label><inputtype="text"class="form-control"id="validationTooltip01"placeholder="First name"value="Mark"required><divclass="valid-tooltip">
Looks good!
<divclass="col-md-4 mb-3"><labelfor="validationTooltip02">Last name</label><inputtype="text"class="form-control"id="validationTooltip02"placeholder="Last name"value="Otto"required><divclass="valid-tooltip">
Looks good!
<divclass="col-md-4 mb-3"><labelfor="validationTooltipUsername">Username</label><divclass="input-group"><divclass="input-group-prepend"><spanclass="input-group-text"id="validationTooltipUsernamePrepend">@</span><inputtype="text"class="form-control"id="validationTooltipUsername"placeholder="Username"aria-describedby="validationTooltipUsernamePrepend"required><divclass="invalid-tooltip">
Please choose a unique and valid username.
<divclass="form-row"><divclass="col-md-6 mb-3"><labelfor="validationTooltip03">City</label><inputtype="text"class="form-control"id="validationTooltip03"placeholder="City"required><divclass="invalid-tooltip">
Please provide a valid city.
<divclass="col-md-3 mb-3"><labelfor="validationTooltip04">State</label><inputtype="text"class="form-control"id="validationTooltip04"placeholder="State"required><divclass="invalid-tooltip">
Please provide a valid state.
<divclass="col-md-3 mb-3"><labelfor="validationTooltip05">Zip</label><inputtype="text"class="form-control"id="validationTooltip05"placeholder="Zip"required><divclass="invalid-tooltip">
Please provide a valid zip.
<buttonclass="btn btn-primary"type="submit">Submit form</button></form>
Custom forms
For even more customization and cross browser consistency, use our completely custom form elements to replace the browser defaults. They’re built on top of semantic and accessible markup, so they’re solid replacements for any default form control.
Checkboxes and radios
Each checkbox and radio
<input>
and
<label>
pairing is wrapped in a
<div>
to create our custom control. Structurally, this is the same approach as our default
.form-check
.
We use the sibling selector (
~
) for all our
<input>
states—like
:checked
—to properly style our custom form indicator. When combined with the
.custom-control-label
class, we can also style the text for each item based on the
<input>
’s state.
We hide the default
<input>
with
opacity
and use the
.custom-control-label
to build a new custom form indicator in its place with
::before
and
::after
. Unfortunately we can’t build a custom one from just the
<input>
because CSS’s
content
doesn’t work on that element.
In the checked states, we use
base64 embedded SVG icons
from
Open Iconic
. This provides us the best control for styling and positioning across browsers and devices.
Checkboxes
<divclass="custom-control custom-checkbox"><inputtype="checkbox"class="custom-control-input"id="customCheck1"><labelclass="custom-control-label"for="customCheck1">Check this custom checkbox</label>
Custom checkboxes can also utilize the :indeterminate pseudo class when manually set via JavaScript (there is no available HTML attribute for specifying it).
If you’re using jQuery, something like this should suffice:
$('.your-checkbox').prop('indeterminate',true)
Radios
<divclass="custom-control custom-radio"><inputtype="radio"id="customRadio1"name="customRadio"class="custom-control-input"><labelclass="custom-control-label"for="customRadio1">Toggle this custom radio</label><divclass="custom-control custom-radio"><inputtype="radio"id="customRadio2"name="customRadio"class="custom-control-input"><labelclass="custom-control-label"for="customRadio2">Or toggle this other custom radio</label>
Inline
<divclass="custom-control custom-radio custom-control-inline"><inputtype="radio"id="customRadioInline1"name="customRadioInline1"class="custom-control-input"><labelclass="custom-control-label"for="customRadioInline1">Toggle this custom radio</label><divclass="custom-control custom-radio custom-control-inline"><inputtype="radio"id="customRadioInline2"name="customRadioInline1"class="custom-control-input"><labelclass="custom-control-label"for="customRadioInline2">Or toggle this other custom radio</label>
Disabled
Custom checkboxes and radios can also be disabled. Add the disabled boolean attribute to the <input> and the custom indicator and label description will be automatically styled.
<divclass="custom-control custom-checkbox"><inputtype="checkbox"class="custom-control-input"id="customCheckDisabled1"disabled><labelclass="custom-control-label"for="customCheckDisabled1">Check this custom checkbox</label><divclass="custom-control custom-radio"><inputtype="radio"name="radioDisabled"id="customRadioDisabled2"class="custom-control-input"disabled><labelclass="custom-control-label"for="customRadioDisabled2">Toggle this custom radio</label>
Switches
A switch has the markup of a custom checkbox but uses the .custom-switch class to render a toggle switch. Switches also support the disabled attribute.
<divclass="custom-control custom-switch"><inputtype="checkbox"class="custom-control-input"id="customSwitch1"><labelclass="custom-control-label"for="customSwitch1">Toggle this switch element</label><divclass="custom-control custom-switch"><inputtype="checkbox"class="custom-control-input"disabledid="customSwitch2"><labelclass="custom-control-label"for="customSwitch2">Disabled switch element</label>
Select menu
Custom <select> menus need only a custom class, .custom-select to trigger the custom styles. Custom styles are limited to the <select>’s initial appearance and cannot modify the <option>s due to browser limitations.
<selectclass="custom-select"><optionselected>Open this select menu</option><optionvalue="1">One</option><optionvalue="2">Two</option><optionvalue="3">Three</option></select>
You may also choose from small and large custom selects to match our similarly sized text inputs.
<selectclass="custom-select custom-select-lg mb-3"><optionselected>Open this select menu</option><optionvalue="1">One</option><optionvalue="2">Two</option><optionvalue="3">Three</option></select><selectclass="custom-select custom-select-sm"><optionselected>Open this select menu</option><optionvalue="1">One</option><optionvalue="2">Two</option><optionvalue="3">Three</option></select>
The multiple attribute is also supported:
<selectclass="custom-select"multiple><optionselected>Open this select menu</option><optionvalue="1">One</option><optionvalue="2">Two</option><optionvalue="3">Three</option></select>
As is the size attribute:
<selectclass="custom-select"size="3"><optionselected>Open this select menu</option><optionvalue="1">One</option><optionvalue="2">Two</option><optionvalue="3">Three</option></select>
Range
Create custom <input type="range"> controls with .custom-range. The track (the background) and thumb (the value) are both styled to appear the same across browsers. As only IE and Firefox support “filling” their track from the left or right of the thumb as a means to visually indicate progress, we do not currently support it.
By default, range inputs “snap” to integer values. To change this, you can specify a step value. In the example below, we double the number of steps by using step="0.5".
The recommended plugin to animate custom file input: bs-custom-file-input, that’s what we are using currently here in our docs.
The file input is the most gnarly of the bunch and requires additional JavaScript if you’d like to hook them up with functional Choose file… and selected file name text.
We hide the default file <input> via opacity and instead style the <label>. The button is generated and positioned with ::after. Lastly, we declare a width and height on the <input> for proper spacing for surrounding content.
Translating or customizing the strings with SCSS
The :lang() pseudo-class is used to allow for translation of the “Browse” text into other languages. Override or add entries to the $custom-file-text Sass variable with the relevant language tag and localized strings. The English strings can be customized the same way. For example, here’s how one might add a Spanish translation (Spanish’s language code is es):
$custom-file-text:(en:"Browse",es:"Elegir"
Here’s lang(es) in action on the custom file input for a Spanish translation:
You’ll need to set the language of your document (or subtree thereof) correctly in order for the correct text to be shown. This can be done using the lang attribute on the <html> element or the Content-Language HTTP header, among other methods.
Translating or customizing the strings with HTML
Bootstrap also provides a way to translate the “Browse” text in HTML with the data-browse attribute which can be added to the custom input label (example in Dutch):
<divclass="custom-file"><inputtype="file"class="custom-file-input"id="customFileLangHTML"><labelclass="custom-file-label"for="customFileLangHTML"data-browse="Bestand kiezen">Voeg je document toe</label>
