这是一个很好的半跨浏览器的方法，有渐变边界，淡出一半。只需将颜色停止设置为rgba(0,0,0,0)

.fade-out-borders {
min-height: 200px; /* for example */

-webkit-border-image: -webkit-gradient(linear, 0 0, 0 50%, from(black), to(rgba(0, 0, 0, 0))) 1 100%;
-webkit-border-image: -webkit-linear-gradient(black, rgba(0, 0, 0, 0) 50%) 1 100%;
-moz-border-image: -moz-linear-gradient(black, rgba(0, 0, 0, 0) 50%) 1 100%;
-o-border-image: -o-linear-gradient(black, rgba(0, 0, 0, 0) 50%) 1 100%;
border-image: linear-gradient(to bottom, black, rgba(0, 0, 0, 0) 50%) 1 100%;
}

<div class="fade-out-border"></div>

用法解释:

Formal grammar: linear-gradient(  [ <angle> | to <side-or-corner> ,]? <color-stop> [, <color-stop>]+ )
                              \---------------------------------/ \----------------------------/
                                Definition of the gradient line         List of color stops  

更多信息请点击:https://developer.mozilla.org/en-US/docs/Web/CSS/linear-gradient

Mozilla目前只支持CSS渐变作为background-image属性的值，以及在简写背景中。

——https://developer.mozilla.org/en/CSS/-moz-linear-gradient

Example 3 - Gradient Borders

border: 8px solid #000;
-moz-border-bottom-colors: #555 #666 #777 #888 #999 #aaa #bbb #ccc;
-moz-border-top-colors: #555 #666 #777 #888 #999 #aaa #bbb #ccc;
-moz-border-left-colors: #555 #666 #777 #888 #999 #aaa #bbb #ccc;
-moz-border-right-colors: #555 #666 #777 #888 #999 #aaa #bbb #ccc;
padding: 5px 5px 5px 15px; 

——http://www.cssportal.com/css3-preview/borders.htm

这是一个带有透明背景的渐变边界，使用边界半径

.gradient-border {
  border-radius: 999px;
  padding: 10px 3rem;
  display: inline-block;
  position: relative;
  background: transparent;
  border: none;
}

.gradient-border::before {
  content: "";
  position: absolute;
  inset: 0;
  padding: 2px;
  border-radius: 9999px;
  background: linear-gradient(87.36deg, blue 6.42%, red 84.24%),
linear-gradient(0deg, #FFFFFF, #FFFFFF);
  -webkit-mask: 
     linear-gradient(#fff 0 0) content-box, 
     linear-gradient(#fff 0 0);
          mask: 
     linear-gradient(#fff 0 0) content-box, 
     linear-gradient(#fff 0 0);
  -webkit-mask-composite: xor;
          mask-composite: exclude;
}

现场演示:https://jsfiddle.net/jbernier/0eypxc74/1/

我同意szajmon的观点。他和昆汀回答的唯一问题是跨浏览器兼容性。

HTML:

<div class="g">
    <div>bla</div>
</div>

CSS:

.g {
background-image: -webkit-linear-gradient(300deg, white, black, white); /* webkit browsers (Chrome & Safari) */
background-image: -moz-linear-gradient(300deg, white, black, white); /* Mozilla browsers (Firefox) */
filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#ffffff', endColorstr='#000000', gradientType='1'); /* Internet Explorer */
background-image: -o-linear-gradient(300deg,rgb(255,255,255),rgb(0,0,0) 50%,rgb(255,255,255) 100%); /* Opera */
}

.g > div { background: #fff; }

试试这个，对我很管用。

div { border - radius: 20 px; 身高:70 vh; 溢出:隐藏; ｝ {前div:: 内容:”; 显示:块; box-sizing: border-box; 高度:100%; 边框:1em实心透明; 边界图像:线性渐变(到顶部，红色0%，蓝色100%); border-image-slice: 1; ｝ < div > < / div >

这是小提琴的链接 https://jsfiddle.net/yash009/kayjqve3/1/希望这对你有所帮助

border-image属性可以实现这一点。您还需要指定border-style和border-width。

border-image: linear-gradient(#f6b73c, #4d9f0c) 30;
border-width: 4px;
border-style: solid;

在MDN上阅读更多。