<resolution>

The <resolution> CSS data type, used in media queries, denotes the density of pixels of an output device, i.e., its resolution.

On screens, the length is related to CSS inches, centimeters, or pixels, not on physical values.

Syntax

The <resolution> data type consists of a <number> immediately followed by a unit of resolution (dpi, dpcm, ...). As with all dimensions, there is no space between the unit literal and the number.

Although the number 0 is always the same regardless of unit, the unit may not be omitted. In other words, 0 is invalid and does not represent 0dpi, 0dpcm, or 0dppx.

Units

dpi: Represents the number of dots per inch. A screen typically contains 72 or 96 dpi, but a printed document usually has much greater dpi. As 1 inch is 2.54 cm, 1dpi ≈ 0.39dpcm.
dpcm: Represents the number of dots per centimeter. As 1 inch is 2.54 cm, 1dpcm ≈ 2.54dpi.
dppx: Represents the number of dots per px unit. Due to the 1:96 fixed ratio of CSS in to CSS px, 1dppx is equivalent to 96dpi, which corresponds to the default resolution of images displayed in CSS as defined by image-resolution.

Examples

Valid examples

96dpi
50dpcm
3dppx
@media print and (min-resolution: 300dpi) { ... }    Correct use in a media query

Invalid examples

72 dpi     Spaces are not allowed between the number and the unit.
ten dpi    The number must use digits only.
0          The unit is required.

Specifications

Specification	Status	Comment
CSS Values and Units Module Level 3 The definition of '<resolution>' in that specification.	Candidate Recommendation	Factorization of the type in a more generic specification. No change
CSS Image Values and Replaced Content Module Level 3 The definition of '<resolution>' in that specification.	Candidate Recommendation	Added the `dppx` unit
Media Queries The definition of '<resolution>' in that specification.	Recommendation	Initial definition

Feature	Chrome	Edge	Firefox (Gecko)	Internet Explorer	Opera	Safari (WebKit)
Basic support	29	20 (12.10240)	3.5 (1.9.1)^[1]	9	9.5	No support^[2]
`dppx`	29	No support	16.0 (16.0)	No support	12.10	?

Feature	Android	Edge	Firefox Mobile (Gecko)	IE Phone	Opera Mobile	Safari Mobile
Basic support	No support^[2]	?	(Yes)	?	(Yes)	No support^[2]
`dppx`	?	?	16.0 (16.0)	?	12.10	?

[1] Before Firefox 8 (Gecko 8.0), it erroneously accepted only CSS dimensions that were <integer> followed by the unit. From that version, it supports any valid CSS dimensions (<number> immediately followed by the unit).

[2] Webkit engine does not support CSS resolution query as in the specification, the use of the non-standard device-pixel-ratio query is needed for browsers Safari, see bug 16832.