Reboot
Reboot, a collection of element-specific CSS changes in a single file, kickstart Bootstrap to provide an elegant, consistent, and simple baseline to build upon.
Approach
Reboot builds upon Normalize, providing many HTML elements with somewhat opinionated styles using only element selectors. Additional styling is done only with classes. For example, we reboot some <table>
styles for a simpler baseline and later provide .table
, .table-bordered
, and more.
Here are our guidelines and reasons for choosing what to override in Reboot:
- Update some browser default values to use
rem
s instead ofem
s for scalable component spacing. - Avoid
margin-top
. Vertical margins can collapse, yielding unexpected results. More importantly though, a single direction ofmargin
is a simpler mental model. - For easier scaling across device sizes, block elements should use
rem
s formargin
s. - Keep declarations of
font
-related properties to a minimum, usinginherit
whenever possible.
Page defaults
The <html>
and <body>
elements are updated to provide better page-wide defaults. More specifically:
- The
box-sizing
is globally set on every element—including*::before
and*::after
, toborder-box
. This ensures that the declared width of element is never exceeded due to padding or border. - No base
font-size
is declared on the<html>
, but16px
is assumed (the browser default).font-size: 1rem
is applied on the<body>
for easy responsive type-scaling via media queries while respecting user preferences and ensuring a more accessible approach. - The
<body>
also sets a globalfont-family
,line-height
, andtext-align
. This is inherited later by some form elements to prevent font inconsistencies. - For safety, the
<body>
has a declaredbackground-color
, defaulting to#fff
.
native font stack
The default web fonts (Helvetica Neue, Helvetica, and Arial) have been dropped in Bootstrap 4 and replaced with a “native font stack” for optimum text rendering on every device and OS. Read more about native font stacks in this Smashing Magazine article .
$font-family-sans-serif:
// Safari for macOS and iOS (San Francisco)
-apple-system,
// Chrome < 56 for macOS (San Francisco)
BlinkMacSystemFont,
// Windows
"Segoe UI",
// Android
Roboto,
// Basic web fallback
"Helvetica Neue", Arial,
// Linux
"Noto Sans",
"Liberation Sans",
// Sans serif fallback
sans-serif,
// Emoji fonts
"Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji" !default;
Note that because the font stack includes emoji fonts, many common symbol/dingbat Unicode characters will be rendered as multi-colored pictographs. Their appearance will vary, depending on the style used in the browser/platform's native emoji font, and they won't be affected by any CSS color
styles.
This font-family
is applied to the <body>
and automatically inherited globally throughout Bootstrap. To switch the global font-family
, update $font-family-base
and recompile Bootstrap.
Headings and paragraphs
All heading elements—eg, <h1>
—and <p>
are reset to have their margin-top
removed. Headings have margin-bottom: .5rem
added and paragraphs margin-bottom: 1rem
for easy spacing.
heading | example |
---|---|
<h1></h1> |
h1. Bootstrap heading |
<h2></h2> |
h2. Bootstrap heading |
<h3></h3> |
h3. Bootstrap heading |
<h4></h4> |
h4. Bootstrap heading |
<h5></h5> |
h5. Bootstrap heading |
<h6></h6> |
h6. Bootstrap heading |
Lists
All lists— <ul>
, <ol>
, and <dl>
—have their margin-top
removed and a margin-bottom: 1rem
. Nested lists have no margin-bottom
.
- All lists have their top margins removed
- And their bottom margin normalized
- Nested lists have no bottom margin
- This way they have a more even appearance
- Particularly when followed by more list items
- The left padding has also been reset
- Here's an ordered list
- With a few list items
- It has the same overall look
- As the previous unordered list
For simpler styling, clear hierarchy, and better spacing, description lists have updated margin
s. <dd>
s reset margin-left
to 0
and add margin-bottom: .5rem
. <dt>
s are bolded .
- Description lists
- A description list is perfect for defining terms.
- Term
- Definition for the term.
- A second definition for the same term.
- Another term
- Definition for this other term.
Preformatted text
The <pre>
element is reset to remove its margin-top
and use rem
units for its margin-bottom
.
.example-element { margin-bottom: 1rem; }
tables
Tables are slightly adjusted to style <caption>
s, collapse borders, and ensure consistent text-align
throughout. Additional changes for borders, padding, and more come with the .table
class .
table heading | table heading | table heading | table heading |
---|---|---|---|
table cell | table cell | table cell | table cell |
table cell | table cell | table cell | table cell |
table cell | table cell | table cell | table cell |
Forms
Various form elements have been rebooted for simpler base styles. Here are some of the most notable changes:
<fieldset>
s have no borders, padding, or margin so they can be easily used as wrappers for individual inputs or groups of inputs.<legend>
s, like fieldsets, have also been restyled to be displayed as a heading of sorts.<label>
s are set todisplay: inline-block
allowmargin
to be applied.<input>
s,<select>
s,<textarea>
s, and<button>
s are mostly addressed by Normalize, but Reboot removes theirmargin
and setsline-height: inherit
, too.<textarea>
s are modified to only be resizable vertically as horizontal resizing often “breaks” page layout.<button>
s and<input>
button elements havecursor: pointer
when:not(:disabled)
.
These changes, and more, are demonstrated below.
Pointers on buttons
Reboot includes an enhancement for role="button"
to change the default cursor to pointer
. Add this attribute to elements to help indicate elements are interactive. This role isn't necessary for <button>
elements, which get their own cursor
change.
<span role="button" tabindex="0">Non-button element button</span>
misc elements
address
The <address>
element is updated to reset the browser default font-style
from italic
to normal
. line-height
is also now inherited, and margin-bottom: 1rem
has been added. <address>
s are for presenting contact information for the nearest ancestor (or an entire body of work). Preserve formatting by ending lines with <br>
.
1355 Market St, Suite 900
San Francisco, CA 94103
P: (123) 456-7890 Full Name
[email protected]
Blockquote
The default margin
on blockquotes is 1em 40px
, so we reset that to 0 0 1rem
for something more consistent with other elements.
A well-known quote, contained in a blockquote element.
Inline elements
The <abbr>
element receives basic styling to make it stand out amongst paragraph text.
Summary
The default cursor
on summary is text
, so we reset that pointer
to convey that the element can be interacted with by clicking on it.
Some details
More info about the details.
Even more details
Here are even more details about the details.
HTML5 [hidden]
attributes
HTML5 adds a new global attribute named[hidden]
, which is styled as display: none
by default. Borrowing an idea from PureCSS , we improve upon this default by making [hidden] { display: none !important; }
to help prevent its display
from getting accidentally overridden. While [hidden]
isn't natively supported by IE10, the explicit declaration in our CSS gets around that problem.
<input type="text" hidden>
jQuery incompatibility
[hidden]
is not compatible with jQuery's $(...).hide()
and $(...).show()
methods. Therefore, we don't currently especially endorse [hidden]
over other techniques for managing the display
of elements.
To simply toggle the visibility of an element, meaning its display
is not modified and the element can still affect the flow of the document, use the .invisible
class instead.