Polygon border of a button with transparent background

Question

I am trying to make a polygon border shape like the image below but with a transparent background.

The code I have tried is below. In the code, there are a total of 28 points. First from a point in left in the clockwise direction, then from the same point in the anti-clockwise direction.

@import url('https://fonts.googleapis.com/css2?family=Poppins&display=swap');

.p-button{
  text-decoration: none;
  background: transparent;
  color: white;
  padding: 14px 50px;
  text-transform: uppercase;
  font-family: "Poppins";
  border: solid 1px black;
  border-radius: 30px;
  font-size:12px;
  --b: 1px; /* border width */
  --h:25px; /* this is half the height, adjust it based on your code */
  clip-path:polygon(
    
    /* 1st to 14th point in anticlockwise direction */
    0 50%,
    calc(0.134*var(--h))  25%,   /* 0.134 = 1 - cos(30)   */
    calc(  0.5*var(--h))  6.7%,  /* 6.7% = 0.134/2 * 100% */
    var(--h) 0,
    calc(100% - var(--h)) 0,
    calc(100% - 0.5*var(--h))   6.7%,
    calc(100% - 0.134*var(--h)) 25%,
    100% 50%,
    calc(100% - 0.134*var(--h)) 75%,
    calc(100% - 0.5*var(--h))   93.3%, /* 93.3% = 100% - 6.7% */
    calc(100% - var(--h)) 100%,
    var(--h) 100%,
    calc(  0.5*var(--h))  93.3%,
    calc(0.134*var(--h))  75%,
    
    
    /* 15th to 28th point in anticlockwise direction */
    calc((0.134*var(--h)) + var(--b))  75%,
    calc((0.5*var(--h)) + var(--b))  93.3%,
    var(--h) calc(100% - var(--b)),
    calc(100% - var(--h)) calc(100% - var(--b)),
    calc(100% - (0.5*var(--h) + var(--b)))   93.3%, /* 93.3% = 100% - 6.7% */
    calc(100% - (0.134*var(--h) + var(--b))) 75%,
    calc(100% - var(--b)) 50%,
    calc(100% - (0.134*var(--h) + var(--b))) 25%,
    calc(100% - (0.5*var(--h) + var(--b)))   6.7%,
    calc(100% - var(--h)) var(--b),
    var(--h) calc(0px + var(--b)),
    calc(  (0.5*var(--h)) + var(--b))  6.7%,  /* 6.7% = 0.134/2 * 100% */
    calc((0.134*var(--h)) + var(--b))  25%,   /* 0.134 = 1 - cos(30)   */
    var(--b) 50%) ;
}

body{
  display: flex;
  height: 100vh;
  align-items: center;
  justify-content: center;
  
}

<a class="p-button" href="">Demo it</a>

The code I took reference for the button with background color (not transparent) is from this link.

@import url('https://fonts.googleapis.com/css2?family=Poppins&display=swap');

.p-button{
  text-decoration: none;
  background: #000;
  color: white;
  padding: 15px 50px;
  text-transform: uppercase;
  font-family: "Poppins";
  font-size:40px;
  --h:45px; /* this is half the height, adjust it based on your code */
  clip-path:polygon(
    0 50%,
    calc(0.134*var(--h))  25%,   /* 0.134 = 1 - cos(30)   */
    calc(  0.5*var(--h))  6.7%,  /* 6.7% = 0.134/2 * 100% */
    var(--h) 0,
    calc(100% - var(--h)) 0,
    calc(100% - 0.5*var(--h))   6.7%,
    calc(100% - 0.134*var(--h)) 25%,
    100% 50%,
    calc(100% - 0.134*var(--h)) 75%,
    calc(100% - 0.5*var(--h))   93.3%, /* 93.3% = 100% - 6.7% */
    calc(100% - var(--h)) 100%,
    var(--h) 100%,
    calc(  0.5*var(--h))  93.3%,
    calc(0.134*var(--h))  75%);
}

body{
  display: flex;
  height: 100vh;
  align-items: center;
  justify-content: center;
  
}

<a class="p-button" href="">Demo it</a>

Is there a reason for not drawing using an SVG? (And if you want to clip the shape as well, doing that slightly outside?) — A Haworth, Jul 26 '21 at 08:13
I tried but, SVG is not responsive like the button. In SVG, it is hard to control padding-left, right, top, and bottom individually. — Foss Bytes, Jul 26 '21 at 08:20
I was thinking of usin the svg as background, or drawn behind the button, not that it would also contain the text and padding. — A Haworth, Jul 26 '21 at 08:25

score 2 · Accepted Answer · answered Jul 26 '21 at 10:07

Your idea is good but you will need to fix the math which is the complex part here.

You will notice that this will also affect the content so I add it as pseudo element to avoid this:

.p-button {
  position:relative;
  padding: 14px 50px;
  font-size:45px;
  text-decoration:none;
}

.p-button:before{
  content:"";
  position:absolute;
  inset:0;
  background:black;
  --b: 4px; /* border width */
  --h:34px; /* this is half the height, adjust it based on your code */
  --b1: calc(0.866*var(--b));
  --b2: calc(0.5*var(--b)); 
  clip-path:polygon(
    
    0 50%,
    calc(0.134*var(--h))  25%,   /* 0.134 = 1 - cos(30)   */
    calc(  0.5*var(--h))  6.7%,  /* 6.7% = 0.134/2 * 100% */
    var(--h) 0,
    calc(100% - var(--h)) 0,
    calc(100% - 0.5*var(--h))   6.7%,
    calc(100% - 0.134*var(--h)) 25%,
    100% 50%,
    calc(100% - 0.134*var(--h)) 75%,
    calc(100% - 0.5*var(--h))   93.3%, /* 93.3% = 100% - 6.7% */
    calc(100% - var(--h)) 100%,
    var(--h) 100%,
    calc(  0.5*var(--h))  93.3%,
    calc(0.134*var(--h))  75%,
    0 50%,
    
    var(--b) 50%,
    calc(0.134*var(--h) + var(--b1))  calc(75% - var(--b2)),
    calc(  0.5*var(--h) + var(--b2))  calc(93.3% - var(--b1)),
    var(--h) calc(100% - var(--b)),
    calc(100% - var(--h)) calc(100% - var(--b)),
    calc(100% - 0.5*var(--h)  - var(--b2))  calc(93.3% - var(--b1)),
    calc(100% - 0.134*var(--h) - var(--b1)) calc(75% - var(--b2)),
    calc(100% - var(--b)) 50%,
    calc(100% - 0.134*var(--h) - var(--b1)) calc(25% + var(--b2)),
    calc(100% - 0.5*var(--h)  - var(--b2))  calc(6.7% + var(--b1)),
    calc(100% - var(--h)) var(--b),
    var(--h) var(--b),
    calc(  0.5*var(--h) + var(--b2))  calc(6.7% + var(--b1)),  
    calc(0.134*var(--h) + var(--b1))  calc(25% + var(--b2)),   
    var(--b) 50%) ;
}

body{
  display: flex;
  height: 100vh;
  align-items: center;
  justify-content: center;
  background:linear-gradient(45deg,red,lightblue);
}

<a class="p-button" href="">Demo it</a>

This is amazing, I didn't think that way. Is there an easier way to achieve this kind of border, maybe via other CSS property I am unknown of? — Foss Bytes, Jul 26 '21 at 14:31
@FossBytes not really, this is probably the most suitable CSS solution. Any other CSS solution will have the same (or more) complexity. — Temani Afif, Jul 26 '21 at 14:49
Also, how have you come up with the formula for clip paths in both buttons? any idea? . I would like to understand more about it. — Foss Bytes, Jul 26 '21 at 18:00
@FossBytes a pen, a paper and some math background. you have 8 points drawn in a circle so with some trigonometry we can get the values (some sin() and cos()). I will try to edit the post later if I get a chance but I cannot promise (it would take time to draw figures and explain) — Temani Afif, Jul 26 '21 at 19:16

score 1 · Answer 2 · answered Jul 26 '21 at 05:20

Here u need is Clipping tool When when using clipping , the border also get clipped so , so inorder to get border we need to add one more div in background with needed border-color and clip that also.. But u cant achieve transparent border along with this method

@import url('https://fonts.googleapis.com/css2?family=Poppins&display=swap');

.p-button{
  text-decoration: none;
  background: white;
  color: black;
  padding: 15px 50px;
  text-transform: uppercase;
  font-family: "Poppins";
  font-size:40px;
  width:260px;
height:94px;
  
 

-webkit-clip-path: polygon(20% 0, 10% 7%, 3% 23%, 0 50%, 3% 75%, 10% 90%, 20% 100%, 80% 100%, 90% 94%, 97% 78%, 100% 50%, 97% 20%, 90% 6%, 80% 0); clip-path: polygon(20% 0, 10% 7%, 3% 23%, 0 50%, 3% 75%, 10% 90%, 20% 100%, 80% 100%, 90% 94%, 97% 78%, 100% 50%, 97% 20%, 90% 6%, 80% 0);

}
.border{
width:264px;
height:98px;
background-color:black;
 display: flex;
 
  align-items: center;
  justify-content: center;

-webkit-clip-path: polygon(20% 0, 10% 7%, 3% 23%, 0 50%, 3% 75%, 10% 90%, 20% 100%, 80% 100%, 90% 94%, 97% 78%, 100% 50%, 97% 20%, 90% 6%, 80% 0); clip-path: polygon(20% 0, 10% 7%, 3% 23%, 0 50%, 3% 75%, 10% 90%, 20% 100%, 80% 100%, 90% 94%, 97% 78%, 100% 50%, 97% 20%, 90% 6%, 80% 0);
}
*{box-sizing: border-box;}
body{
  display: flex;
  height: 100vh;
  align-items: center;
  justify-content: center;
  
}

<div class="border"><a class="p-button" href="">Demo it</a></div>

score -1 · Answer 3 · answered Jul 26 '21 at 03:58

You cannot get the functionality you want directly from clipping tools. Because they are made for another purpose.

A workaround would be:

.polygon {
  display: inline-block;
  position: relative;
  width: 150px;
  height: 150px;
  background: red;
  box-sizing: border-box;
  -webkit-clip-path: polygon(92.32051% 40%, 93.79385% 43.1596%, 94.69616% 46.52704%, 95% 50%, 94.69616% 53.47296%, 93.79385% 56.8404%, 92.32051% 60%, 79.82051% 81.65064%, 77.82089% 84.50639%, 75.35575% 86.97152%, 72.5% 88.97114%, 69.3404% 90.44449%, 65.97296% 91.34679%, 62.5% 91.65064%, 37.5% 91.65064%, 34.02704% 91.34679%, 30.6596% 90.44449%, 27.5% 88.97114%, 24.64425% 86.97152%, 22.17911% 84.50639%, 20.17949% 81.65064%, 7.67949% 60%, 6.20615% 56.8404%, 5.30384% 53.47296%, 5% 50%, 5.30384% 46.52704%, 6.20615% 43.1596%, 7.67949% 40%, 20.17949% 18.34936%, 22.17911% 15.49361%, 24.64425% 13.02848%, 27.5% 11.02886%, 30.6596% 9.55551%, 34.02704% 8.65321%, 37.5% 8.34936%, 62.5% 8.34936%, 65.97296% 8.65321%, 69.3404% 9.55551%, 72.5% 11.02886%, 75.35575% 13.02848%, 77.82089% 15.49361%, 79.82051% 18.34936%);
  clip-path: polygon(92.32051% 40%, 93.79385% 43.1596%, 94.69616% 46.52704%, 95% 50%, 94.69616% 53.47296%, 93.79385% 56.8404%, 92.32051% 60%, 79.82051% 81.65064%, 77.82089% 84.50639%, 75.35575% 86.97152%, 72.5% 88.97114%, 69.3404% 90.44449%, 65.97296% 91.34679%, 62.5% 91.65064%, 37.5% 91.65064%, 34.02704% 91.34679%, 30.6596% 90.44449%, 27.5% 88.97114%, 24.64425% 86.97152%, 22.17911% 84.50639%, 20.17949% 81.65064%, 7.67949% 60%, 6.20615% 56.8404%, 5.30384% 53.47296%, 5% 50%, 5.30384% 46.52704%, 6.20615% 43.1596%, 7.67949% 40%, 20.17949% 18.34936%, 22.17911% 15.49361%, 24.64425% 13.02848%, 27.5% 11.02886%, 30.6596% 9.55551%, 34.02704% 8.65321%, 37.5% 8.34936%, 62.5% 8.34936%, 65.97296% 8.65321%, 69.3404% 9.55551%, 72.5% 11.02886%, 75.35575% 13.02848%, 77.82089% 15.49361%, 79.82051% 18.34936%);
}
.polygon img {
  position: absolute;
  top: 2px; /* equal to border thickness */
  left: 2px; /* equal to border thickness */
  width: 146px; /* container height - (border thickness * 2) */
  height: 146px; /* container height - (border thickness * 2) */
  -webkit-clip-path: polygon(92.32051% 40%, 93.79385% 43.1596%, 94.69616% 46.52704%, 95% 50%, 94.69616% 53.47296%, 93.79385% 56.8404%, 92.32051% 60%, 79.82051% 81.65064%, 77.82089% 84.50639%, 75.35575% 86.97152%, 72.5% 88.97114%, 69.3404% 90.44449%, 65.97296% 91.34679%, 62.5% 91.65064%, 37.5% 91.65064%, 34.02704% 91.34679%, 30.6596% 90.44449%, 27.5% 88.97114%, 24.64425% 86.97152%, 22.17911% 84.50639%, 20.17949% 81.65064%, 7.67949% 60%, 6.20615% 56.8404%, 5.30384% 53.47296%, 5% 50%, 5.30384% 46.52704%, 6.20615% 43.1596%, 7.67949% 40%, 20.17949% 18.34936%, 22.17911% 15.49361%, 24.64425% 13.02848%, 27.5% 11.02886%, 30.6596% 9.55551%, 34.02704% 8.65321%, 37.5% 8.34936%, 62.5% 8.34936%, 65.97296% 8.65321%, 69.3404% 9.55551%, 72.5% 11.02886%, 75.35575% 13.02848%, 77.82089% 15.49361%, 79.82051% 18.34936%);
  clip-path: polygon(92.32051% 40%, 93.79385% 43.1596%, 94.69616% 46.52704%, 95% 50%, 94.69616% 53.47296%, 93.79385% 56.8404%, 92.32051% 60%, 79.82051% 81.65064%, 77.82089% 84.50639%, 75.35575% 86.97152%, 72.5% 88.97114%, 69.3404% 90.44449%, 65.97296% 91.34679%, 62.5% 91.65064%, 37.5% 91.65064%, 34.02704% 91.34679%, 30.6596% 90.44449%, 27.5% 88.97114%, 24.64425% 86.97152%, 22.17911% 84.50639%, 20.17949% 81.65064%, 7.67949% 60%, 6.20615% 56.8404%, 5.30384% 53.47296%, 5% 50%, 5.30384% 46.52704%, 6.20615% 43.1596%, 7.67949% 40%, 20.17949% 18.34936%, 22.17911% 15.49361%, 24.64425% 13.02848%, 27.5% 11.02886%, 30.6596% 9.55551%, 34.02704% 8.65321%, 37.5% 8.34936%, 62.5% 8.34936%, 65.97296% 8.65321%, 69.3404% 9.55551%, 72.5% 11.02886%, 75.35575% 13.02848%, 77.82089% 15.49361%, 79.82051% 18.34936%);
}

<div class="polygon">
  <img src="http://lorempixel.com/g/600/400/">
</div>

Or perhaps having two clipping polygons on top of each other to mimic transparency. For further details refer to this post.

Polygon border of a button with transparent background

3 Answers3