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Browsers' default CSS for HTML elements

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What is the default value for any HTML element?

Browsers assign default values to properties on HTML elements. For example, the <body> element has a default margin of 10px .

What is default HTML?

The HTML default Attribute is a Boolean attribute. This attribute is used to specify that the track will be enabled if the user's preferences do not indicate that another track would be more appropriate. Note: With a default attribute, there must not be more than one track element per media element.

How do I restore the default property value in CSS?

In short, there's no easy way to restore to default values to whatever a browser uses . The closest option is to use the 'initial' property value, which will restore it to the default CSS values, rather than the browser's default styles.


It's different for each browser, so:

  • Firefox (Gecko): https://dxr.mozilla.org/mozilla-central/source/layout/style/res/html.css. Or, browse to resource://gre-resources/ and look at html.css.
  • Chrome/Safari (WebKit): http://trac.webkit.org/browser/trunk/Source/WebCore/css/html.css
    • Chrome (Blink): https://chromium.googlesource.com/chromium/blink/+/master/Source/core/css/html.css
  • Internet Explorer (Trident), older versions: http://web.archive.org/web/20170122223926/http://www.iecss.com/

You can also look at the HTML5 Boilerplate stylesheet, which "normalizes the display of a lot of stuff without being a reset in the traditional sense". It also fixes quite a few bugs/inconsistencies.

It's also worth looking at: https://github.com/necolas/normalize.css/blob/master/normalize.css


A GitHub repository of all W3C HTML spec and vendor default CSS stylesheets can be found here

1. Default Styles for Firefox

2. Default Styles for Internet Explorer

3. Default Styles for Chrome / Webkit

4. Default Styles for Opera

5. Default Styles for HTML4 (W3C spec)

6. Default Styles for HTML5 (W3C spec)

Sample, per the default W3C HTML4 spec:

html, address,
blockquote,
body, dd, div,
dl, dt, fieldset, form,
frame, frameset,
h1, h2, h3, h4,
h5, h6, noframes,
ol, p, ul, center,
dir, hr, menu, pre   { display: block; unicode-bidi: embed }
li              { display: list-item }
head            { display: none }
table           { display: table }
tr              { display: table-row }
thead           { display: table-header-group }
tbody           { display: table-row-group }
tfoot           { display: table-footer-group }
col             { display: table-column }
colgroup        { display: table-column-group }
td, th          { display: table-cell }
caption         { display: table-caption }
th              { font-weight: bolder; text-align: center }
caption         { text-align: center }
body            { margin: 8px }
h1              { font-size: 2em; margin: .67em 0 }
h2              { font-size: 1.5em; margin: .75em 0 }
h3              { font-size: 1.17em; margin: .83em 0 }
h4, p,
blockquote, ul,
fieldset, form,
ol, dl, dir,
menu            { margin: 1.12em 0 }
h5              { font-size: .83em; margin: 1.5em 0 }
h6              { font-size: .75em; margin: 1.67em 0 }
h1, h2, h3, h4,
h5, h6, b,
strong          { font-weight: bolder }
blockquote      { margin-left: 40px; margin-right: 40px }
i, cite, em,
var, address    { font-style: italic }
pre, tt, code,
kbd, samp       { font-family: monospace }
pre             { white-space: pre }
button, textarea,
input, select   { display: inline-block }
big             { font-size: 1.17em }
small, sub, sup { font-size: .83em }
sub             { vertical-align: sub }
sup             { vertical-align: super }
table           { border-spacing: 2px; }
thead, tbody,
tfoot           { vertical-align: middle }
td, th, tr      { vertical-align: inherit }
s, strike, del  { text-decoration: line-through }
hr              { border: 1px inset }
ol, ul, dir,
menu, dd        { margin-left: 40px }
ol              { list-style-type: decimal }
ol ul, ul ol,
ul ul, ol ol    { margin-top: 0; margin-bottom: 0 }
u, ins          { text-decoration: underline }
br:before       { content: "\A"; white-space: pre-line }
center          { text-align: center }
:link, :visited { text-decoration: underline }
:focus          { outline: thin dotted invert }

/* Begin bidirectionality settings (do not change) */
BDO[DIR="ltr"]  { direction: ltr; unicode-bidi: bidi-override }
BDO[DIR="rtl"]  { direction: rtl; unicode-bidi: bidi-override }

*[DIR="ltr"]    { direction: ltr; unicode-bidi: embed }
*[DIR="rtl"]    { direction: rtl; unicode-bidi: embed }

@media print {
  h1            { page-break-before: always }
  h1, h2, h3,
  h4, h5, h6    { page-break-after: avoid }
  ul, ol, dl    { page-break-before: avoid }
}

No one has mentioned any source for the CSS defaults in Edge. I looked, and I couldn't find anything authoritative, but I found this stylesheet that looks plausible: https://gist.github.com/jonathantneal/abc52743caa0a019d359ec4ba2ce965b