What exactly is needed for margin 0 auto to work

Question

I know that setting margin  0 auto  on an element is used to centre it  left-right   However  I know that the element and its parent must meet certain criteria for the auto margin to work  and I can never seem to get the magic right   So my question is simple  what CSS properties have to be set on an element and its parent in order for margin  0 auto  to left-right centre the child

User · Answer

Off the top of my head  if the element is not a block element - make it so   and then give it a width

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It will also work with display table - a useful display property in this case because it doesn t require a width to be set   I know this post is 5 years old  but it s still relevant to passers-by

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Here is my Suggestion   First         1  Add display  block or table       2  Add position  relative       3  Add width  percentage also works fine  Second         if above trick not works then you have to add float none

User · Answer

Off the top of my cat s head  make sure the div you re trying to center is not set to width  100    If it is  then the rules set on the child divs are what will matter

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Please go to this quick example I ve created jsFiddle  Hopefull it s easy to understand  You can use a wrapper div with the width of the site to center align  The reason you must put width is that so browser knows you are not going for a liquid layout

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Complete rule for CSS     display  block AND width not auto  OR display  table float  none position  relative

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Off the top of my head    The element must be block-level  e g  display  block or display  table The element must not float The element must not have a fixed or absolute position1   Off the top of other people s heads    The element must have a width that is not auto2   Note that all of these conditions must be true of the element being centered for it to work     1 There is one exception to this  if your fixed or absolutely positioned element has left  0  right  0  it will center with auto margins   2 Technically  margin  0 auto does work with an auto width  but the auto width takes precedence over the auto margins  and the auto margins are zeroed out as a result  making it seem as though they  don t work

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Off the top of my head  it needs a width  You need to specify the width of the container you are centering  not the parent width

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It s perhaps interesting that you do not have to specify width for a  lt button gt  element to make it work - just make sure it has display block   http   jsfiddle net muhuyttr

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For anybody just now hitting this question  and not being able to fix margin  0 auto  here s something I discovered you may find useful  a table element with no specified width must have display  table and not display  block in order for margin  auto to do work  This may be obvious to some  as the combination of display  block and the default width value will give a table which expands to fill its container  but if you want the table to take it s  natural  width and be centered  you need display  table

[css] What, exactly, is needed for "margin: 0 auto;" to work?

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