How do I make a CSS triangle with smooth edges?

Question

I have a triangle (JSFiddle) using this CSS:

.triangle {
    width: 0;
    height: 0;
    border-top: 0;
    border-bottom: 30px solid #666699;
    border-left: 20px solid transparent; 
    border-right: 20px solid transparent;
    }

And this HTML:

<div class="triangle"></div>

This makes a triangle, but the diagonal lines are jagged and pixelated. How can I make them smooth? (I was able to smooth them out in Safari and Chrome by making them dotted, but that broke the triangles in Firefox and IE.)

Answer 1

Even in pure CSS we can get the smooth diagonals.

.triangle {
    width: 0;
    height: 0;
    border-top: 0;
    border-bottom: 30px solid #666699;
    border-left: 20px solid rgba(255, 255, 255, 0); 
    border-right: 20px solid rgba(255, 255, 255, 0);
}

Instead of giving transparent you can make use of rgba(255, 255, 255, 0). This again gives transparent. But the alpha=0 makes smooth diagonals.

Check the browser support for rgba css-tricks.com/rgba-browser-support

Thanks

Answer 2

For me, using dashed for the transparent borders worked for most browsers that don't automatically smooth them and rotating 360 degrees worked for old Webkit:

.triangle {
    width: 0;
    height: 0;
    border-top: 0;
    border-bottom: 30px solid #666699;
    border-left: 20px dashed transparent; 
    border-right: 20px dashed transparent;
    -webkit-transform: rotate(360deg);
}

Answer 3

I have just stumbled upon the same problem, and figured out this trick (at least, it works on a Mac):

-webkit-transform: rotate(0.05deg);
-moz-transform: scale(1.1);
-o-transform: rotate(0.05deg); /* Didn't check Opera yet */
transform: rotate(0.05deg);

Answer 4

A very hacky way would be using a rotated div

Here I used two divs to show a triangle:

<div class="triangle">
    <div class="rot"></div>
</div>

and rotated the inner div for two not right sides of triangle:

.triangle{
    position:relative;
    width:100px;
    height:60px;
    border-bottom:1px solid black;
    border-radius:12px;
}
.rot{
    border-radius:10px;
    border-left: 1px solid black;
border-top: 1px solid black;
width:70px; height:70px;
    -webkit-transform:rotate(45deg);
    position:absolute;
    left:15px;
    top:23px;
}

I didn't tried to find the relation between numbers.

Here is the fiddle of the code:

http://jsfiddle.net/mohsen/HTMcF/

BUT I would strongly suggest you to use canvas element for this reason.

Answer 5

None of the others worked for me, but I found the following did (by accident):

.triangle {
  border: 1.3rem dashed #666699;
  border-right: .5rem solid rgba(255, 255, 255, 0);
}

The mixture of dashed/solid and the rgba fix worked in FF31, IE11, and Chrome36.

Answer 6

For Firefox you can add -moz-transform: scale(.9999); to make smooth edges. In your case:

.triangle {
    width: 0;
    height: 0;
    border-top: 0;
    border-bottom: 30px solid #666699;
    border-left: 20px solid transparent; 
    border-right: 20px solid transparent;
    -moz-transform: scale(.9999);
}

Will do the trick.