Centering in CSS: A Complete Guide
Centering things in CSS is the poster child of CSS complaining. Why does it have to be so hard? They jeer. I think the issue isn’t that it’s difficult to do, but in that there so many different ways of doing it, depending on the situation, it’s hard to know which to reach for. So let’s make it a decision tree and hopefully make it easier. I need to center…
Is it inline or inline-* elements (like text or links)? You can center inline elements horizontally, within a block-level parent element, with just:
This will work for inline, inline-block, inline-table, inline-flex, etc. Is it a block level element? You can center a block-level element by giving it margin-left and margin-right of auto (and it has a set width , otherwise it would be full width and wouldn’t need centering). That’s often done with shorthand like this:
This will work no matter what the width of the block level element you’re centering, or the parent. Note that you can’t float an element to the center. There is a trick though. Is there more than one block level element? If you have two or more block-level elements that need to be centered horizontally in a row, chances are you’d be better served making them a different display type. Here’s an example of making them inline-block and an example of flexbox:
Unless you mean you have multiple block level elements stacked on top of each other, in which case the auto margin technique is still fine:
Vertical centering is a bit trickier in CSS. Is it inline or inline-* elements (like text or links)? Is it a single line? Sometimes inline / text elements can appear vertically centered, just because there is equal padding above and below them.
If padding isn’t an option for some reason, and you’re trying to center some text that you know will not wrap, there is a trick were making the line-height equal to the height will center the text.
Is it multiple lines? Equal padding on top and bottom can give the centered effect for multiple lines of text too, but if that isn’t going to work, perhaps the element the text is in can be a table cell, either literally or made to behave like one with CSS. The vertical-align property handles this, in this case, unlike what it normally does which is handle the alignment of elements aligned on a row. (More on that.)
If something table-like is out, perhaps you could use flexbox? A single flex-child can be made to center in a flex-parent pretty easily.
Remember that it’s only really relevant if the parent container has a fixed height (px, %, etc), which is why the container here has a height. If both of these techniques are out, you could employ the “ghost element” technique, in which a full-height pseudo-element is placed inside the container and the text is vertically aligned with that.
.ghost-center < position: relative; >.ghost-center::before < content: " "; display: inline-block; height: 100%; width: 1%; vertical-align: middle; >.ghost-center p
Is it a block-level element? Do you know the height of the element? It’s fairly common to not know the height in web page layout, for lots of reasons: if the width changes, text reflow can change the height. Variance in the styling of text can change the height. Variance in the amount of text can change the height. Elements with a fixed aspect ratio, like images, can change height when resized. Etc. But if you do know the height, you can center vertically like:
Is the element of unknown height? It’s still possible to center it by nudging it up half of it’s height after bumping it down halfway:
Do you care if the element stretches the height of the container? If you don’t, you just need the content inside vertically centered, using tables or CSS display to make elements into tables can do the trick.
Both Horizontally & Vertically
You can combine the techniques above in any fashion to get perfectly centered elements. But I find this generally falls into three camps: Is the element of fixed width and height? Using negative margins equal to half of that width and height, after you’ve absolutely positioned it at 50% / 50% will center it with great cross-browser support:
Is the element of unknown width and height? If you don’t know the width or height, you can use the transform property and a negative translate of 50% in both directions (it is based on the current width/height of the element) to center:
Can you use flexbox? To center in both directions with flexbox, you need to use two centering properties:
Can you use grid? This is just a little trick (sent in by Lance Janssen) that will pretty much work for one element:
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Comments
Good idea! I like the concept of this article and also the show/hide structure. I applaud you, sir. However, I think you’re missing the spirit behind the classic “centering is hard” complaint in a couple of places, which, at least for me, always comes back to not knowing the height of the elements. 1) Your display: table-cell fix relies on knowing the height of the child element. 2) In your “is it block level” -> “is the element of unknown height” you proceed to give the parent an explicit height. To me, that defeats the purpose of trying to handle the unknown-height scenario. If I don’t know the height of the child, it’s quite common for me to also not know the height of the parent. 3) In your “both hor & vert example” where the height is unknown, it’s a little weird to have the child be pos: absolute and imply that this is no big deal. I think pos: absolute is a major caveat when laying things out, since it can have the unintended consequence of having elements layer over one another. 4) Also, in that same pen, the element fails to stay vertically centered if it has a sibling that stretches the vertical height of the parent. Regardless, I still really like the idea of this –it’s sorely needed. I just think it would be improved if you acknowledged some of the caveats that I think are at the root of the complaint you’re trying to dismiss.
1) It doesn’t actually. I updated the example to put the height on the table instead. 2) Vertical centering is only relevant if the parent has a set height. If the parent doesn’t have a set height, what are you centering within? Even if the answer is “the entire page”, then you need to set the height of (probably) both html, body 3) That’s fair. It’s just one example. In my experience, if you’re trying to center something both ways like that, it’s probably a modal, in which the absolute (or fixed) positioning is going to be used. If it’s not, you can combine any of the other techniques as needed. And there is always flexbox which I covered a bunch. 4) Demo me on this one? I’m having a hard time picturing/reproducing.
Web Style Sheets CSS tips & tricks
The most common and (therefore) easiest type of centering is that of lines of text in a paragraph or in a heading. CSS has the property ‘text-align’ for that:
renders each line in a P or in a H2 centered between its margins, like this:
The lines in this paragraph are all centered between the paragraph’s margins, thanks to the value ‘center’ of the CSS property ‘text-align’.
Centering a block or image
Sometimes it is not the text that needs to be centered, but the block as a whole. Or, phrased differently: we want the left and right margin to be equal. The way to do that is to set the margins to ‘auto’. This is normally used with a block of fixed width, because if the block itself is flexible, it will simply take up all the available width. Here is an example:
This rather narrow block of text is centered. Note that the lines inside the block are not centered (they are left-aligned), unlike in the earlier example.
This is also the way to center an image: make it into block of its own and apply the margin properties to it. For example:
The following image is centered:
Centering vertically
CSS level 2 doesn’t have a property for centering things vertically. There will probably be one in CSS level 3 (see below ). But even in CSS2 you can center blocks vertically, by combining a few properties. The trick is to specify that the outer block is to be formatted as a table cell, because the contents of a table cell can be centered vertically.
DIV.container < min-height: 10em; display: table-cell; vertical-align: middle >.This small paragraph.
This small paragraph is vertically centered.
Centering vertically in CSS level 3
CSS level 3 offers other possibilities. At this time (2014), a good way to center blocks vertically without using absolute positioning (which may cause overlapping text) is still under discussion. But if you know that overlapping text will not be a problem in your document, you can use the ‘transform’ property to center an absolutely positioned element. For example:
This paragraph is vertically centered.
For a document that looks like this:
the style sheet looks like this:
div.container3 < height: 10em; position: relative > /* 1 */ div.container3 p < margin: 0; position: absolute; /* 2 */ top: 50%; /* 3 */ transform: translate(0, -50%) > /* 4 */
- Make the container relatively positioned, which declares it to be a container for absolutely positioned elements.
- Make the element itself absolutely positioned.
- Place it halfway down the container with ‘top: 50%’. (Note that 50%’ here means 50% of the height of the container.)
- Use a translation to move the element up by half its own height. (The ‘50%’ in ‘translate(0, -50%)’ refers to the height of the element itself.)
Recently (since about 2015), another technique has also become available in several CSS implementations. It is based on the new ‘flex’ keyword for the ‘display’ property. This keyword is meant for use in graphical user interfaces (GUIs), but nothing stops you from using it in a document, if the document happens to have the right structure.
This paragraph is vertically centered.
the style sheet looks like this:
div.container5 < height: 10em; display: flex; align-items: center > div.container5 p
Centering vertically and horizontally in CSS level 3
We can extend both methods to center horizontally and vertically at the same time.
A side-effect of making the paragraph absolutely positioned is that it is then only as wide as it needs to be (unless we give it an explicit width, of course). In the example below, that’s precisely what we want: We center a paragraph with just one word (“Centered!”), so the width of the paragraph should be exactly the width of that word.
The yellow background is there to show that the paragraph is indeed only as wide as its contents. We assume the same mark-up as before:
The style sheet is similar to the previous example with respect to the vertical centering. But we now move the element halfway across the container as well, with ‘left: 50%’, and at the same time move it leftwards by half its own width in the ‘translate’ transformation:
div.container4 < height: 10em; position: relative >div.container4 p < margin: 0; background: yellow; position: absolute; top: 50%; left: 50%; margin-right: -50%; transform: translate(-50%, -50%) >
The next example below explains why the ‘margin-right: -50%’ is needed.
When the CSS formatter supports ‘flex’, it’s even easier:
div.container6 < height: 10em; display: flex; align-items: center; justify-content: center > div.container6 p
i.e., the only addition is the ‘justify-content: center’. Just like ‘align-items’ determines the vertical alignment of the container’s contents, ‘justify-content’ determines the horizontal alignment. (It’s actually a bit more complex, as their names suggest, but in a simple case that’s how it works.) A side-effect of ‘flex’ is that the child element, the P in this case, is automatically made as small as possible.
Centering in the viewport in CSS level 3
The default container for absolutely positioned elements is the viewport. (In case of a browser, that means the browser window). So centering an element in the viewport is very simple. Here is a complete example. (This example uses HTML5 syntax.)
Nicely centered
This text block is vertically centered.
Horizontally, too, if the window is wide enough.
You can see the result in a separate document.
The ‘margin-right: -50%’ is needed to compensate the ‘left: 50%’. The ‘left’ rule reduces the available width for the element by 50%. The renderer will thus try to make lines that are no longer than half the width of the container. By saying that the right margin of the element is further to the right by that same amount, the maximum line length is again the same as the container’s width.
Try resizing the window: You’ll see that each sentence is on one line when the window is wide enough. Only when the window is too narrow for the whole sentence will the sentence be broken over several lines. When you remove the ‘margin-right: -50%’ and resize the window again, you’ll see that the sentences will be broken already when the window is still twice as wide as the text lines.
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Bert Bos, style activity lead
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Created 5 May 2001;
Last updated Wed 06 Jan 2021 05:40:49 AM UTC