The ConstrainDouble type is used to specify a constraint for a property whose value is a double-precision floating-point number. It extends the DoubleRange dictionary (which provides the ability to specify a permitted range of property values) to also support an exact value and/or an ideal value the property should take on. Additionally, you can specify the property's value as a simple floating-point value, in which case the user agent does its best to match the value once all other more stringent constraints are met.


If the value of a ConstrainDouble is an object rather than a number, it may have the properties below in addition the properties it inherits from DoubleRange.

A double-precision floating-point number specifying a specific, required, value the property must have to be considered acceptable.
A double-precision floating-point number specifying a value the property would ideally have, but which can be considered optional if necessary to find a match.


Specification Status Comment
Media Capture and Streams
The definition of 'ConstrainDouble' in that specification.
Candidate Recommendation Initial definition

Technically, ConstrainDouble is actually based on an intermediary dictionary named ConstrainDoubleRange, which adds exact and ideal to DoubleRange, with ConstrainDouble being a type that can be either a long integer or a DoubleRange. However, for the sake of documentation clarity, the intermediate type (present only because of quirks in WebIDL syntax) is ignored here.

Browser compatibility

ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
ConstrainDoubleChrome Full support YesEdge Full support ≤79Firefox Full support 50IE No support NoOpera Full support YesSafari ? WebView Android Full support YesChrome Android Full support YesFirefox Android Full support 50Opera Android Full support YesSafari iOS ? Samsung Internet Android Full support Yes


Full support
Full support
No support
No support
Compatibility unknown
Compatibility unknown

See also