filter

CSS Filters are a powerful tool that authors can use to achieve varying visual effects (sort of like Photoshop filters for the browser). The CSS filter property provides access to effects like blur or color shifting on an element’s rendering before the element is displayed. Filters are commonly used to adjust the rendering of an image, a background, or a border.

The syntax is:

.filter-me {
  filter: blur(3px);
  filter: grayscale(1);
  filter: saturate(2.2);

  filter: none; /* remove existing filter */
}

There are a number of functions to use for the value:

• blur()
• brightness()
• contrast()
• drop-shadow()
• grayscale()
• hue-rotate()
• invert()
• opacity()
• saturate()
• sepia()
• url() – for applying SVG filters
• custom() – “coming soon”

Multiple functions can be used, space separated.

.do-more-things {
  filter: blur(20px) grayscale(20%);
}

Filter Functions

To use the CSS filter property, you specify a value for one of the following functions listed above. If the value is invalid, the function returns “none.” Except where noted, the functions that take a value expressed with a percent sign (as in 34%) also accept the value expressed as decimal (as in 0.34).

Here’s a demo that lets you play with individual filters a bit:

grayscale()

filter: grayscale(20%)

/* same as... */
filter: grayscale(0.2);

Converts the input image to grayscale. The value of “amount” defines the proportion of the conversion. A value of 100% is completely grayscale. A value of 0% leaves the input unchanged. Values between 0% and 100% are linear multipliers on the effect. If the “amount” parameter is missing, a value of 100% is used. Negative values are not allowed.

sepia()

filter: sepia(0.8);

/* same as... */
filter: sepia(80%);

Converts the input image to sepia. The value of “amount” defines the proportion of the conversion. A value of 100% is completely sepia. A value of 0 leaves the input unchanged. Values between 0% and 100% are linear multipliers on the effect. If the “amount” parameter is missing, a value of 100% is used. Negative values are not allowed.

saturate()

filter: saturate(2);

/* same as... */
filter: saturate(200%);

Saturates the input image. The value of “amount” defines the proportion of the conversion. A value of 0% is completely un-saturated. A value of 100% leaves the input unchanged. Other values are linear multipliers on the effect. Values over 100% are allowed, providing super-saturated results. If the “amount” parameter is missing, a value of 100% is used. Negative values are not allowed.

hue-rotate()

filter: hue-rotate(180deg);

/* same as... */
filter: hue-rotate(0.5turn);

Applies a hue rotation on the input image. The value of “angle” defines the number of degrees around the color circle the input samples will be adjusted. A value of 0deg leaves the input unchanged. If the “angle” parameter is missing, a value of 0deg is used. The maximum value is 360deg.

invert()

filter: invert(100%);

Inverts the samples in the input image. The value of “amount” defines the proportion of the conversion. A value of 100% is completely inverted. A value of 0% leaves the input unchanged. Values between 0% and 100% are linear multipliers on the effect. If the “amount” parameter is missing, a value of 100% is used. Negative values are not allowed.

opacity()

filter: opacity(0.5);

/* same as... */
filter: opacity(50%);

Applies transparency to the samples in the input image. The value of “amount” defines the proportion of the conversion. A value of 0% is completely transparent. A value of 100% leaves the input unchanged. Values between 0% and 100% are linear multipliers on the effect. This is equivalent to multiplying the input image samples by amount. If the “amount” parameter is missing, a value of 100% is used. This function is similar to the more established opacity property; the difference is that with filters, some browsers provide hardware acceleration for better performance. Negative values are not allowed.

brightness()

filter: brightness(0.5);

/* same as... */
filter: brightness(50%);

Applies a linear multiplier to input image, making it appear more or less bright. A value of 0% will create an image that is completely black. A value of 100% leaves the input unchanged. Other values are linear multipliers on the effect. Values of an amount over 100% are allowed, providing brighter results. If the “amount” parameter is missing, a value of 100% is used.

contrast()

filter: contrast(4);

/* same as... */
filter: contrast(400%);

Adjusts the contrast of the input. A value of 0% will create an image that is completely black. A value of 100% leaves the input unchanged. Values over the amount over 100% are allowed, providing results with less contrast. If the “amount” parameter is missing, a value of 100% is used.

blur()

filter: blur(5px);
filter: blur(1rem);

Applies a Gaussian blur to the input image. The value of ‘radius’ defines the value of the standard deviation to the Gaussian function, or how many pixels on the screen blend into each other, so a larger value will create more blur. If no parameter is provided, then a value 0 is used. The parameter is specified as a CSS length, but does not accept percentage values.

drop-shadow()

filter: drop-shadow(2px 2px 5px rgb(0 0 0 / 0.5));
filter: drop-shadow(4px 4px red); /* no blur */

Applies a drop shadow effect to the input image. A drop shadow is effectively a blurred, offset version of the input image’s alpha mask drawn in a particular color, composited below the image. The function accepts a parameter of type (defined in CSS3 Backgrounds), with the exception that the ‘inset’ keyword is not allowed.

This function is similar to the more established box-shadow property; the difference is that with filters, some browsers provide hardware acceleration for better performance.

Drop-shadow also mimics the intended objects outline naturally unlike box-shadow that treats only the box as its path.

Just like with text-shadow, there is no ‘spread’ parameter to create a solid shadow larger than the object.

url()

filter: url()

The url() function takes the location of an XML file that specifies an SVG filter, and may include an anchor to a specific filter element. Here’s a tutorial that works as a nice intro to SVG filters with a fun demo.

Animating Filters

Since Filters are animatable it can open the doors for a whole bunch of fun.

Notes

You may combine any number of functions to manipulate the rendering, but order still matters (i.e., using grayscale() after sepia() will result in completely gray output).

A computed value of other than “none” results in the creation of a stacking context the same way that CSS opacity does. The filter property has no effect on the geometry of the target element’s box model, even though filters can cause painting outside of an element’s border box. Any parts of the target element are affected by filter functions. This includes any content, background, borders, text decoration, outline and visible scrolling mechanism of the element to which the filter is applied, and those of its descendants. Filters can also be applied to inline content, such as individual text spans.

The specification also introduces a filter(image-URL, filter-functions) wrapper function for an image. It would allow you to filter any image at the time you use it within CSS. For example, you could blur a background image without blurring the text. This filter function is not yet supported in browsers. In the meantime, you can apply both the background and the filter to a pseudo-element to create a similar effect.

The IE proprietary filter stuff

Also used the filter property, like:

.half-opacity {
  -ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=50)";
  filter: alpha(opacity=50);
}

Mostly used for opacity when you needed to support IE 8 and down.

More Information

• W3C Filter Effects Specification
• Bennett Feely’s Filters Gallery
• MDN Docs
• CSS Filters polyfill
• Understanding CSS Filter Effects

Browser Support