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Summary
The <frequency> CSS data type denotes a frequency dimension, like the pitch of a speaking voice. It consists of a <number> immediately followed by the unit. Like for any CSS dimension, there is no space between the unit literal and the number.
The following units may be used:
Hzwhich represents a frequency in Hertz. E.g.0Hz,1500Hz,10000Hz.kHzwhich represents a frequency in kilohertz. E.g.0kHz,1.5kHz,10kHz.
Even if all units represent the same time for the value 0, the unit may not be omitted in that case as it isn't a <length>: 0 is invalid and does not represent 0Hz, 0kHz. Though the units are case-insensitive in CSS, it is good practice to use a capital H for Hz and kHz, as in the SI, Hertz being a family noun.
Examples
| Code | Meaning |
|---|---|
12Hz |
Positive integer. |
-456kHz |
Negative integer. |
4.3Hz |
Non-integer. |
14KhZ |
The unit is case-insensitive, though non-SI capitalization is not recommended. |
+0Hz |
Zero, with a leading + and the unit. |
-0kHz |
Zero, with a leading - and the unit (Though strange, this is an allowed value). |
| Code | Meaning |
|---|---|
12.0 |
This is a <number>, not an <frequency>, it must have a unit. |
7 Hz |
No space is allowed between the <number> and the unit. |
0 |
Zero values can be written without a unit only if there are <length> values, not <frequency>. |
Specifications
| Specification | Status | Comment |
|---|---|---|
| CSS Values and Units Module Level 3 The definition of '<frequency>' in that specification. |
Candidate Recommendation | Initial definition |
This data type was initially introduced in CSS Level 2 for the now obsoleted aural media group, where it was used to define the pitch of the voice. This has been deprecated since then, but the <frequency> data type has been reintroduced in CSS3, though no CSS property is using it at the moment.
Browser compatibility
| Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
|---|---|---|---|---|---|
| Basic support | No support | No support | No support | No support[1] | No support |
| Feature | Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|
| Basic support | No support | No support | No support | No support | No support |
[1] Some versions of Opera may have (partial) support for the obsolete aural media group, and through the pitch property support for the <frequency> data type.