CSS Triangles

Discussion

1. Alex Simon

   whoa! what am I missing here? – where are the browser hacks, the js, etc?
   Surly it can’t be that easy!
2. iamunr

   @Alex Simon: That’s exactly what I was thinking! This is weird, incredible, and I can’t figure out why it’s working.
3. Jacob Rask

   It’s a 0 pixel element in the middle, and browsers render border edges slanted which creates the border. It’s a great trick indeed. You can also do it with pseudo-elements, something like this:

   
.tooltip:before {
content: '';
display: block;
width: 0;
height: 0;
border: 5px solid;
border-color: #2f2f2f transparent transparent;
}

4. digibomb

   Awesomeness!!! Can’t wait to try this with a slider i’m working on. Perfect for the next, prev buttons…
5. Krystian

   It seems that CSS is more and more self-sufficient. Great example, thanks.
6. Binyamin

   For IE6 you need to use in css color, transparent does not work.
7. Ivan

   You should also check — http://tantek.com/CSS/Examples/polygons.html and http://www.russellheimlich.com/blog/pure-css-shapes-triangles-delicious-logo-and-hearts/ , with the former being really profound.
8. Dr. Azrael Tod

   WTF?
   Way better then my previous Solution (before-content set to unicode-Triangles), although i have to admit its pretty hard to understand why it works that way.
   Still.. have to try this in my private projects.
9. Eric Wendelin

   Wait a minute Walsh, so you DIDN’T read my blog post about this months ago? Now I’m just a bit sad…
10. David Walsh

    @Eric Wendelin: Mine is more focused on the triangle itself, plus you wrote that in Feb. I dont’ remember what *I* wrote in February.
11. Sunny Singh

    I’ve been using this for at least a year now so it’s nothing new and requires no special CSS3 or anything. Nice to have a good resource for them though, I always use them for dropdowns and what not.
12. Jesse G. Donat

    I’ve been using CSS triangles on my site http://donatstudios.com for quite a while – notice on the right under the headers, the little triangle – I hate images and that was a nice way around it.
13. Christoph Pojer

    Just for the fun of it: http://jsfiddle.net/bRwmk/
14. Jesse G. Donat

    Also I, based http://jsfiddle.net/Fk3Kj/ on the concept a back in February

    @Jesse G. Donat:
15. fakedarren

    It’s easier to visualise when you see this:

    http://jsfiddle.net/ctCXY/

    The font-size of 0px (or line-height: 0px, or overflow: hidden) may be needed for IE6 in some cases.
16. Danz

    I looked at how the borders are created and it makes sense as to why it would result in a triangular look. I continuously get designs with a lot triangles. Ingenious! Thanks for the tip!
17. Eric M Wendelin

    @David Walsh: Heh, no worries :)

    Do you get the idea that CSS is getting much more verbose lately?
• David Walsh

  A bit. I’m just glad the we seem to be moving forward.
18. David Workman

    Great :) Took me a minute or so to figure out why it worked like that but not a trick I’ll be forgetting in a hurry :)

    For those still wondering why it works, do the following:

    – Draw a square on a piece of paper
    – Draw in the diagonals of the square so you have a box made of 4 triangles.

    What you have on the paper in front of you now is the border regions of a 0x0 element in the CSS model.
19. TheToolman

    I saw this technique quite a long time ago on this 3D javascript demo:

    http://www.uselesspickles.com/triangles/demo.html

    The link above shows how triangles of arbitrary shape can be made from a group of these right angle triangles.
20. cancel bubble

    There’s more info on this here (courtesy of Jon Rohan), http://www.dinnermint.org/css/creating-triangles-in-css/

    “Few people realize when a browser draws the borders, it draws them at angles. This technique takes advantage of that. One side of the border is colored for the color of the arrow, and the rest are transparent. Then you set the width of the border to something large”

    Hedger Wang also recently posted this, http://hedgerwow.appspot.com/demo/arrows which looks like you no longer need a filter for transparency in IE.
• David Walsh

  Thank you for the reference material! :)
21. Cipa

    How about some css shadows?
22. Cipa

    Do css shadows work on those triangles?
23. Dan

    Wow, that’s neat

    Thanks for the great tip
24. Matt Barnes

    For anyone who has to deal with IE6, this technique will work in that browser if you give the borders a color instead of having them be transparent.
25. dougwig

    Nice! —the same idea could be extended to create a “V” shape ( for tooltips, etc.) by positioning a second smaller triangle on top if the first ( say a white triangle on top of a larger black triangle ).
26. Michael

    You should add line-height: 0; font-size: 0; for IE, especially if you are supporting v6
• David Walsh

  Good point Michael – updated!
27. Jonathan

    I can’t believe no-one’s mentioned CSS Play yet – Stu’s done some crazy stuff with borders in the page, check out this flag! http://www.cssplay.co.uk/menu/flag

    If you’ve not been there before, check out his demos – they’ve been around for about 4+ years now I think but are still really fun to dissect with Firebug.
28. Dutchie

    Yea, CSS FTW I say, f#ck JS
29. Jean-Philippe HALIMI

    Still, there is a problem with this technique ; it seems there is no way to add borders to the triangle. Anyway, nice trick, indeed :o)
• Jesse G. Donat

  You could totally just position a slightly larger triangle behind it.
• David Walsh

  You beat me to this one! :)
30. Alejandro Briz

    Amazing !!
    ¡¡ Increíble tío !!
31. Pedro Duarte

    /* IE6 */
.chat-bubble-arrow {
_border-left-color: pink;
_border-bottom-color: pink;
_border-right-color: pink;
_filter: chroma(color=pink);
}
32. abidibo

    Also take a look at the control bar of this html5 player
    http://videojs.com/
    all html+css, same methods.. bye!
33. Lachlann

    Great trick, has any one else tried creating an isosceles triangle by adjusting the border sizes? works fine in Firefox but looks very pixelated in chrome safari

    Any ideas?

    L
34. Ben Atkin

    It says div.arrow-left twice in your example css.
35. Juan Mendes

    This is cool, but not new. A co-worker of mine came up with this technique about 4 years ago, he even has a workaround for versions of IE that don’t support transparent borders. Check out his example of 3d rendering using triangles http://www.uselesspickles.com/triangles/ His blog also has a better visual explanation of how the transparent borders make the div become a triangle, this post keeps it a mistery.
36. Daniel Buchner

    In case anyone was annoyed by the tiny dark outline that browsers leave around the edges of CSS triangles such as these, you can set the border-style of the transparent borders to dotted and it will make them go away ;)
• KTB

  Thank you very much.
37. Daniel Buchner

    Oh, and on browsers that support rgba(), setting the transparent border side colors to rgba(255, 255, 255, 0) works as well.
• Danielle Kinney

  Daniel,

  You are a amazing!

  I have been searching for a solution to the dark outline issue in FF.

  THANK YOU SO MUCH!
38. Joe Twumasi

    Wow David this works perfectly across browser. Nice
39. Shawn Sweeney

    I’m using a similar method, but using the pseduo element before to add the arrow. Can’t get the arrow to show up in IE 8. Ever run in this?
40. Britto

    Works perfectly.. Thx
41. Person

    Open sans is terrible, completely terrible.
42. Dr. Clue

    While most folks gained their first excitment using CSS triangles to dispose of images, now the fun part is with CSS3 and actually using the same border arrow trick , but this time with the border image property to texturize the triangles in 3D, to make cool egyption pyramids.

    Just remember when you put your texture togeather that same gets diced up like a tic-tac-toe board and you need them lower left and right squares to be divided diagnally as appropriate for each of the two corners each half transparent and half texture. (Not really hard , just a few minutes in InkScape)
43. Peter Galiba

    The sad thing, if the triangles doesn’t have 45˚ sides it looks really pixelated in Firefox. Other browsers are really fine, specially in mobile Safari, as it can use the retina display to create sharp edges there. It looks the worse on mobile and Windows Firefox, on Mac it is better but still far from ideal. IE, Chrome and Safari looks excellent and the OS doesn’t matter even (where supported) and even non-blink Opera is better.
44. MoOx

    I’ve some CSS shapes into Sass mixins a while ago

    Sass Triangle: https://github.com/MoOx/compass-recipes/blob/master/stylesheets/recipes/shape/polygon/_triangle.scss
    (demos: http://compass-recipes.moox.fr/tests/recipes/shape/polygon/triangle/)

    Sass Tooltip: https://github.com/MoOx/compass-recipes/blob/master/stylesheets/recipes/ui/_tooltip.scss
    (demos: http://compass-recipes.moox.fr/tests/recipes/ui/tooltip/)
45. Mike

    @mixin caret($position, $width, $color) {
    &:after {
    border: $width solid transparent;
    content: ”;
    position: absolute;
    #{$position}: -(2 * $width);

    @if $position == right {
    border-left-color: $color;
    top: 50%;
    @include experimental-value(top, calc(50% – #{$width}));
    }
    @else if $position == left {
    border-right-color: $color;
    top: 50%;
    @include experimental-value(top, calc(50% – #{$width}));
    }

    @else if $position == top {
    border-bottom-color: $color;
    left: 50%;
    @include experimental-value(left, calc(50% – #{$width}));
    }
    @else if $position == bottom {
    border-top-color: $color;
    left: 50%;
    @include experimental-value(left, calc(50% – #{$width}));
    }
    }
    }
46. Florian

    There are so many possibilities of geometric CSS shapes. CSS-Tricks listed some really interesting ones:
    http://www.css-tricks.com/examples/ShapesOfCSS
    Even Yin Yang is among them. ;-)
47. Rahul Kashyap

    only one word for this tutorial it is really “amazing” thanks for this post :)

    Regards
    Rahul Kashyap
48. l3bel

    Great trick, tnx

    (Hope I’m not missing something) I think there is a small typo in the markup of your Pseudo-Element demo ( the enclosing div has id = “position:relative;” should have style=…. )
49. Ted

    There were two major downsides I found with this solution which made me very sad. 1) In certain circumstances (I saw it on high DPI displays) there was a hair’s-width line between the triangle and the attached rectangle. Second, it doesn’t work on display: table-cell, so its use for a row of tabs is limited.
50. Anil Namde

    I am trying to extent it to create image/document section separator (http://tympanus.net/Development/SectionSeparators/) in page. However as we have to mention size in pixel not sure how it would help with responsive design.

    Is there any way it can be extended to fit for responsive design ?
51. Wallbb

    Can this be done with background elements ?
52. Pablo S.

    Great. Someone could describe the advantages of this technique instead of using, let’s say, images?
53. neer

    here is an easy tutorial for this:
    http://sqeets.com/articles/creating-a-triangle-in-html-using-css/
54. Amol Nirmala Waman

    Short and simple Sass mixin example
    http://webdesigncolors.com/css-arrows-sass-mixin/
55. Rashmi

    Its a nice and simple solution. You saved me a lot of headache.
    Thank you.
56. Matt Jennings

    Thank you sir! I’m using a modified version of your code and can confirm it works on IE9 through 11, Edge 12 and 13, Chrome (Mac and Win), Firefox (Mac and Win), and Safari.

    I used https://www.browserstack.com/ to test.
57. Vivek Moyal

    I am using the triangle code with the bootstrap dropdown menu but how i can change the color of the triangle when i hover the first element of the dropdown. Here is the code

    .dropdown-menu::before {
        border-bottom: 15px solid rgba(0, 0, 0, 0.2);
        border-left: 15px solid rgba(0, 0, 0, 0);
        border-right: 15px solid rgba(0, 0, 0, 0);
        content: "";
        display: inline-block;
        left: 20px;
        position: absolute;
        top: -15px;
    }
      .dropdown-menu::after {
        border-bottom:15px solid #FFFFFF;
        border-left:15px solid rgba(0, 0, 0, 0);
        border-right:15px solid rgba(0, 0, 0, 0);
        content: "";
        display: inline-block;
        left: 20px;
        position: absolute;
        top: -14px;
      }
    
58. Lÿo

    Instead of using absolute position, is it possible to center the triangle pointer regardless of the width of the tooltip?
• Lÿo

  Got my answer already thanks.

  margin-left: auto;
  margin-right: auto;
  left: 0;
  right: 0;
  
59. Dennis

    Hey Walsh, i really would like to know exactly why it works. Why giving border to a element with no height or width it draws a triangle? I think it’s awesome, but i dont understang why that happen. Any explanation or reading would be great! thank you! awesome post!