If you have googled this a bit more, you would have found the answer right away.

The box-shadow property syntax is the fallowing :

box-shadow : horizontal offset | vertical offset | blur | spread | color ;

So you want it on all sides means :

  1. No offsets.
  2. Blur as you like.

Spread here is key to this, setting 10px to the spread means 5px on all sides, basically, half the amount will be on each facing side.

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

div {
  padding: 30px;
  margin: 30px;
  width: 300px;
  height: 100px;
  padding: 15px;
  background-color: orange;
  box-shadow: 0px 0px 10px 10px grey;
}
<div></div>

Also if you want to customize that you always define multiple shadows separated by a comma.

Answer from user7148391 on Stack Overflow
๐ŸŒ
W3Schools
w3schools.com โ€บ css โ€บ css3_shadows_box.asp
CSS Box Shadow
The higher the number, the more blurred the shadow will be. A <div> element with a 5px blurred, lightblue box-shadow
Discussions

css - Seamless box-shadow for blurry effect - Stack Overflow
The buggy rendering in Chrome seems ... to only occur with large blur-radius values. Through trial and error you can use the spread-radius to cover up the bug. ... These are the changes that work on your site. Place the border radius and box shadow on the outer div to eliminate ... More on stackoverflow.com
๐ŸŒ stackoverflow.com
html - Box-shadow side-effect blur not smooth. inner square in shadow - Stack Overflow
You can read more about CSS Box shadows in the MDN Documentation ... Sign up to request clarification or add additional context in comments. ... Thakns for your answer @Stewartside. But your code snippet still shows the same effect. (I'm using Chrom browser) 2015-06-15T11:58:28.537Z+00:00 ... @IsraelGav read the explanation. Setting the blur ... More on stackoverflow.com
๐ŸŒ stackoverflow.com
Simple trick to make your box-shadows look much better

I've done graphic design for many years and this applies to anything you want to make a drop shadow for, it requires 4 layers but the effect is flawless in appearance.

Excellent tip for applying this to css.

More on reddit.com
๐ŸŒ r/web_design
50
559
June 21, 2017
Use colored Box Shadow in Tailwind CSS for NProgress Glow effect?
Creator of Tailwind said it's in the works for v3 :) More on reddit.com
๐ŸŒ r/tailwindcss
2
5
April 2, 2021
๐ŸŒ
MDN Web Docs
developer.mozilla.org โ€บ en-US โ€บ docs โ€บ Web โ€บ CSS โ€บ Reference โ€บ Properties โ€บ box-shadow
box-shadow - CSS - MDN Web Docs - Mozilla
January 12, 2026 - If in any pair of shadows, one has inset set and the other does not, the entire shadow list is uninterpolated; the shadows will change to the new values without an animating effect. The box-shadow property enables you to cast a drop shadow from the frame of almost any element.
๐ŸŒ
CSS-Tricks
css-tricks.com โ€บ almanac โ€บ properties โ€บ b โ€บ box-shadow
box-shadow | CSS-Tricks
September 22, 2022 - The vertical offset (required) ... the box. The blur radius (required), if set to 0 the shadow will be sharp, the higher the number, the more blurred it will be, and the further ......
๐ŸŒ
W3Schools
w3schools.com โ€บ cssref โ€บ css3_pr_box-shadow.php
CSS box-shadow property
box-shadow: none|h-offset v-offset blur spread color |inset|initial|inherit; Note: To attach more than one shadow to an element, add a comma-separated list of shadows (see "Try it Yourself" example below). Tip: Read more about allowed values (CSS length units)
๐ŸŒ
Josh W. Comeau
joshwcomeau.com โ€บ css โ€บ designing-shadows
Designing Beautiful Shadows in CSS โ€ข Josh W. Comeau
To ensure consistency, each shadow should use the same ratio between these two numbers. As an element gets closer to the user, the offset should increase, the blur radius should increase, and the shadow's opacity should decrease.
๐ŸŒ
Medium
medium.com โ€บ @nanacodesign โ€บ css-box-shadow-what-is-difference-between-blur-and-spread-c3a3de92a126
CSS box-shadow: blur vs spread | Medium
July 1, 2024 - As you can see above the image, If the blur value increase, the shadow is more blurred. On the other hand, If the spread value increase, the size of the shadow is bigger as the value. Tip1. Multiple shadow ยท Also, you can make multiple shadow like below. It is separated by commas. ... /*..., ..., ...; */.multiple { box-shadow: inset 0 0 0 10px darkred, 0px 0px 0px 10px LightSeaGreen, 20px 20px 0px 10px darkblue; }
Find elsewhere
๐ŸŒ
MDN Web Docs
developer.mozilla.org โ€บ en-US โ€บ docs โ€บ Web โ€บ CSS โ€บ box-shadow
box-shadow - CSS | MDN
If the lists of shadows have different lengths, then the shorter list is padded at the end with shadows whose color is transparent, and X, Y, and blur are 0, with the inset, or lack of inset, being set to match. If in any pair of shadows, one has inset set and the other does not, the entire shadow list is uninterpolated; the shadows will change to the new values without an animating effect. box-shadow = <spread-shadow># <spread-shadow> = <'box-shadow-color'>? && [ <'box-shadow-offset'> [ <'box-shadow-blur'> <'box-shadow-spread'>? ]? ] && <'box-shadow-position'>? <box-shadow-color> = <color># <box-shadow-offset> = [ none | <length>{2} ]# <box-shadow-blur> = <length [0,โˆž]># <box-shadow-spread> = <length># <box-shadow-position> = [ outset | inset ]#
๐ŸŒ
Elektronotdienst-nuernberg
elektronotdienst-nuernberg.de โ€บ bugs โ€บ box-shadow_inset.html
CSS box-shadow "inset" and blur (tests, examples)
Read What does a blur radius mean? from Mozilla's David Baron if you are interested in browser implementation details. ... 0 0 0 1em gold, 0 0 1em 2em red, 0 0 0 3em black, 0 0 0 3.7em yellowgreen, 0 0 0 4.4em green; /* border-radius: 1px */ ... Specifying a color is optional. If omitted, box-shadows are drawn in foreground color (text color), as in the following four examples with dark brown shadows.
๐ŸŒ
GeeksforGeeks
geeksforgeeks.org โ€บ css โ€บ css-box-shadow-property
CSS box-shadow Property - GeeksforGeeks
September 27, 2024 - box-shadow: h-offset v-offset blur-radius spread-radius color | none | inset | initial | inherit; ... In this example, we apply the CSS box-shadow property to two div elements. The first element has a shadow with a horizontal offset of 5px, ...
๐ŸŒ
WebFX
webfx.com โ€บ home โ€บ blog โ€บ web design โ€บ a close look at css box shadow
A Close Look at CSS Box Shadow - WebFX
The blur radius is optional. If you donโ€™t specify it, it will default to 0. Additionally, it canโ€™t have a negative value, unlike horizontal offset and vertical offset. If the blur radius is 0, the box shadow will be sharp and its color will be solid.
๐ŸŒ
Tailwind CSS
tailwindcss.com โ€บ docs โ€บ box-shadow
box-shadow - Effects - Tailwind CSS
By default colored shadows have an opacity of 100% but you can adjust this using the opacity modifier. Use ring or ring-<number> utilities like ring-2 and ring-4 to apply a solid box-shadow to an element:
๐ŸŒ
Refine
refine.dev โ€บ home โ€บ blog โ€บ tutorials โ€บ css box shadow with 25 examples
CSS Box Shadow with 25 Examples | Refine
February 28, 2024 - To apply a box shadow, select an element using the CSS selectors and specify the required horizontal and vertical offsets as above. Optionally, specify the blur and spread radius, box shadow color, and the inset keyword.
๐ŸŒ
SpinKit
tobiasahlin.com โ€บ blog โ€บ layered-smooth-box-shadows
Smoother & sharper shadows with layered box-shadows | Tobias Ahlin
September 19, 2019 - We can achieve this effect by creating multiple box-shadows (separating each shadow with a comma), and increasing the offset and blur for every shadow (the box-shadow syntax is X-offset Y-offset blur color):
๐ŸŒ
W3docs
w3docs.com โ€บ learn-css โ€บ box-shadow.html
CSS box-shadow Property
Positive value gives shadow below the element. Negative values place the shadow above the element. If both values are 0, the shadow will be behind the element. The third value is a blur. The higher the number, the bigger the blur, so the shadow becomes bigger and lighter.
๐ŸŒ
HTML-CSS-JS
html-css-js.com โ€บ css โ€บ generator โ€บ box-shadow
Box Shadow CSS Generator and Style Gallery
Set the properties of your box shadow to get the CSS style. Use the sliders and the color picker to set the values and watch the live preview until you reach the desired effect. Select the right-down shift, spread, blur, opacity, color.
๐ŸŒ
CSS-Tricks
css-tricks.com โ€บ snippets โ€บ css โ€บ css-box-shadow
CSS Box Shadow | CSS-Tricks
September 29, 2022 - -moz-box-shadow: 0px 0px 0px 4px red; -webkit-box-shadow: 0px 0px 0px 4px red; box-shadow: 0px 0px 0px 4px red; Setting the blur to 1px was the closest I could get to solid and still have it render on Android devices:
Top answer
1 of 2
4

For circular box-shadows the blur cannot go above the width & height of the element. The spread can though.

Since your element is 200px * 200px, the maximum for the blur value is 200px.

Have a look below at the example which doesn't go above 200px and you will see that it creates the box-shadow as expected

div {
  width: 200px;
  height: 200px;
  border-radius: 100px;
  background-color: blue;
  box-shadow: 169px 129px 200px -15px rgba(0, 0, 0, 1);
}
<div></div>

The spread value can alternatively go above the element width and height and therefore you can make bigger spreads.

div {
  width: 200px;
  height: 200px;
  border-radius: 100px;
  background-color: blue;
  box-shadow: 169px 129px 0 250px rgba(0, 0, 0, 1);
}
<div></div>

You also didn't really need the prefixes since CSS3 Box-shadows are very well supported now. CanIUse

You can read more about CSS Box shadows in the MDN Documentation

2 of 2
3

If you want to go outside its dimensions on the shape to be blurred:

The code creates a copy of the circle then colours it black and uses the filter:blur(length);

.circle {
  border-radius: 50%;
  width: 100px;
  height: 100px;
  position: relative;
}
.circle::after {
  position: absolute;
  display: block;
  content: " ";
  border-radius: 50%;
  width: 100%;
  height: 100%;
  background-color: blue;
}
.circle::before {
  position: absolute;
  display: block;
  content: " ";
  border-radius: 50%;
  width: 100%;
  height: 100%;
  background-color: black;
  top: 50%;
  left: 50%;
  -webkit-filter: blur(50px);
  filter: blur(50px);
}
<div class="circle"></div>

You can also create inset shadows this way.

How it works: 1. The initial shape is the shadow-color 2. Set overflow:hidden so nothing goes outside the shape. 3. Put a shape on top 4. Blur the shape on top

By doing this the shape under shines through creating the inner shadow effect

.circle {
  border-radius: 50%;
  width: 100px;
  height: 100px;
  position: relative;
  background-color: black;
  overflow: hidden;
}
.circle::before {
  position: absolute;
  display: block;
  content: " ";
  border-radius: 50%;
  width: calc(100%);
  height: calc(100%);
  background-color: blue;
  transform: translate(-50%, -50%);
  top: 50%;
  left: 50%;
  -webkit-filter: blur(20px);
  filter: blur(20px);
}
<div class="circle"></div>