Vertical Centering in CSS

Posted on by mtoplistChuyên mục:Top List

Vertical Centering in CSS

Yuhu’s Definitive Solution with Unknown Height

Though there is a CSS property vertical-align, it doesn’t work like attribute
valign in HTML tables. CSS property vertical-align doesn’t seem to be able to
solely solve this problem:

Definition of the problem

  • there is an area (e.g. <div>) with known height in the page
  • an internal object (typically long text in <div>) is inside the area
    and I don’t know its height (e.g. because its content is
    dynamically generated from a database)
  • I want to center the object vertically within the area
  • without using HTML tables.

No general solution was known until September 2004. I have found it going
home on Wilson street.

Display an
example of the vertical centering in your browser.

Update 2015 – flex

As new browsers support display: flex, it is much easier to vertical
center an item with CSS than before.

<style>
#containter {
    height: 400px;
    display: flex;
    /* flex-direction: column;*/
    align-items: center;
    /* justify-content: center;*/
}
#content {}
</style>

<div id=”containter”>
    <div id=”content”>
        any text<br>
        any height<br>
        any content, for example generated
from DB<br>
        everything is vertically centered
    </div>
</div>

See this example in browser.

Uncommenting justify-content: center or
flex-direction: column you can get other types
of centering (horizontal, both). For instance justify-content: center with
align-items: center leads to centered content both vertically and
horizontally.

The most important rule is display: flex.
This relatively new value switches the display of the
containter to a special mode, enabling its
direct descendant to use and align in all the space of the containter
(using special properties like align-items and
others). The container has set some width, i.e. width: 400px just for
purpose of this example. There is no need to style the content element, but
it must be direct descendant of the container.

Support of display: flex is very good in modern browsers. Last not-supporting
browsers are Internet Explorer 9 and 10 (version 10 has a special syntax of
flex). If it is important for you to optimize for those and older browsers,
you should read the rest of this page.

 

Original content from 2004 with updates:

The idea

The keystone of the solution for Internet Explorer 6, 7 or quirk mode
is this: the internal object is absolutely positioned in half of the area
height. Then is moved up by half of its height. The wrong
interpretation of the height property in older Internet Explorer is used as
a feature here (counted height is taken as a base of percentage height of
nested tags). One extra nested tag <div> is needed for those Explorers.

Solution for standard browsers like Mozilla, Opera, Safari etc. (including
IE 8, 9, 10 and younger) is completely different. Entire area (top <div>) is
set to be displayed as a table (display: table; part of CSS2). The internal
object is set as table-cell (display: table-cell). Now — there is the key
idea — it is possible to use vertical-align property for such table-displayed
element in standard browsers. (Internet Exlorer 6, 7 and quirk mode ignores
those properties or doesn’t know their values.)

Then both syntax are merged. I use the Pixy’s

underscore hack, but with sign #. A CSS property written with the char #
on the start (i.e. #position) is visible for IE 7 and older. Such written
property is invisible for any other standard browser (e.g. Explorer 6 or 7
interprets #position: absolute; unlike other browsers). This so
called “underscore hack” seems to be valid, but if you don’t want to use it,
you may use the more structured code below in my
second example (unfortunately, not working for IE 7). Other types of
browsers and Internet Explorer 8 and younger don’t need to be hacked, as
they support display: table-cell properly.

Compatibility

The code below works in Internet Explorer 5.0, 5.5, 6.0, 7, 8, 9 and 10
beta, in Gecko browsers (Mozilla, Firefox, Netscape 7), in Opera 7, 8 and up,
every Chrome, Konqueror 3.3.1. (maybe lower too), and in Safari (Win, iOS).
The page can be HTML, HTML5 or XHTML, standard or quirk mode.

The valid example doesn’t work in IE 7 standard mode (update 2012: about
3 % of clients). If you find any easy workaround for IE 7, please let me
know.

Understandable code:

<!DOCTYPE HTML>
<html>
<head>
  <title>Universal vertical center with CSS</title>
  <style>
    .greenBorder {border: 1px solid green;} /* just borders
to see it */
  </style>
</head>

<body>
  <div class=”greenBorder” style=”display: table;
height: 400px;
#position: relative;
overflow: hidden;”>
    <div style=” #position: absolute;
#top: 50%;display:
table-cell; vertical-align: middle;”>
      <div class=”greenBorder” style=”
#position: relative;
#top: -50%”>
        any text<br>
        any height<br>
        any content, for example
generated from DB<br>
        everything is vertically centered
      </div>
    </div>
  </div>
</body>
</html>
See this example in
browser

Legend for colors:

CSS styles for every browser
CSS styles for standard browsers
CSS style only for Internet Explorer 6, 7 and quirk (with # hack)

The result looks:

any text
any height
any content, for example generated from DB
everything is vertically centered

See this example in
browser

Let’s make it structural and without hacks

(NOTE: this valid solution described below doesn’t work in Internet Explorer
7 (standard mode), because IE7 doesn’t understand table- values in display
property. The centered object is too high. BUT: IE 7 is used by only about 3
% of users (2012) and the number will decrease. If you still do mind IE7
users, please use the non-valid solution above, write in quirk mode, or use
html conditional comments for separating the properties for IE 7 somehow.)

The first example above is not nice, but I hope you have understood it. It’s
possible to write code differently. For example this way:

<div id=”outer”>
  <div id=”middle”>
    <div id=”inner”>
      any text
      any height
      any content, for example generated from DB
      everything is vertically centered
    </div>
  </div>
</div>

And the structured valid style:

<style type=”text/css”>
#outer {height: 400px; overflow: hidden; position:
relative;}
#outer[id] {display: table; position: static;}

#middle {position: absolute; top: 50%;}
/* for quirk explorer only*/
#middle[id] {display: table-cell; vertical-align:
middle; width: 100%; position: static;}

#inner {position: relative; top: -50%}
/* for quirk explorer only */
/* optional: #inner[id] {position: static;} */
</style>


See the valid
example in browser (it looks the same way as the last one).

Color legend:

CSS style for Internet Explorer 6 only (or quirk)
CSS styles for standard browsers

CSS2 selector #value[id] is equivalent to selector #value,
but Internet Explorer 6 ignores these types of selectors with [id].
Generally: syntax
*[foo] means any element with attribute foo. Any
HTML element #something must have the attribute id by definition set to “something”.
That’s the trick — #value[id] works in standard browsers only
(similarly works .value[class])

There’s CSS property position set to absolute or relative for Internet
Explorer. The code position: static get’s it back to default
value in standard browsers (property top doesn’t work then).

Both vertical and horizontal centering

The core code will be the same, you just need to add some extra CSS rules.
If is your page in standard mode, add this code:

<style>
#outer {width: 100%;}
#inner {width: 200px; margin-left: auto; margin-right: auto;}
</style>

As you probably see, this is the most common horizontal centering method –
auto left and right margin. Because margins needs the space in Firefox and
Opera, you need to set a width to the #outer div. If 100% doesn’t fit your
needs, use any other value.

The important thing is to set some proper width to #inner. This tutorial is
about vertical centering of an object with unknown height. I assume that
you know the width of the object (in most cases you will simply decide
how wide it should be). You may use the pixel values, or the percentage
width. If the centered object is only an unknown-size image, you don’t need
to set width.

If you use quirk mode page rendering (mode depends on !Doctype, as you know),
added code should be a bit longer, because quirk mode of Exploder doesn’t
understand auto margins, but has one nice bug in text-align interpretation
instead. This code should work for both standard and quirk mode:

<style>
#outer {width: 100%;}
#middle {width: 100%; text-align: center;}
#inner {width: 200px; margin-left: auto; margin-right: auto; text-align:
left;}
</style>

Please take note that this is just part of code, which you have to add to
the previous example. If you are lazy to combine codes, please see the
complete example in browser:
vertical
and horizontal centering. You know, I’m lazy too.

How to center vertically on window’s height

The same way, and just add the style:

<style>
body, html {height: 100%;}
#outer {height: 100%; overflow: visible;} /* or without overflow */
...
</style>

It seems that #outer declaration should be sufficient, but it is not. Body
and html declaration sets 100% of the window’s height as a base for next
percentage. Now it is better not to set overflow: hidden (like in the
examples above), because when the content would be taller than window, then
it would be impossible to scroll on.

Related

Previous attempt to center vertically:

Examples:

Read in other language:

Centralizando verticalmente com CSS – Brazilian Portuguese translation of
this article by Maurício Samy Silva

Вертикальне центрування в CSS – Ukrainian translation by Agnessa Petrova
from A2Goos team

Вертикальное центрирование в CSS – Russian translation by Aleksandr Molochan

Czech version of this article
(original, not updated)

All other articles on this website
www.jakpsatweb.cz is in Czech.

About

First published Sep 21, 2004, updated Oct 23, 2006 and May 25 2008. Major
update Dec 6 2012 including bugfix of code in valid example. June 2015 major
update about flex. I’ll update this article with more information if you
wish.

Author:

Dušan Janovský
aka Yuhů
[email protected]
www.jakpsatweb.cz
From Prague, Czech Republic, search algorithms specialist in Seznam.cz
search engine. Wi
Tw
Fb

mtoplist