BaseAudioContext: currentTime property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since April 2021.

The currentTime read-only property of the BaseAudioContext interface returns a double representing an ever-increasing hardware timestamp in seconds that can be used for scheduling audio playback, visualizing timelines, etc. It starts at 0.

Value

A floating point number.

Examples

js
const audioCtx = new AudioContext();
// Older webkit/blink browsers require a prefix

// …

console.log(audioCtx.currentTime);

Reduced time precision

To offer protection against timing attacks and fingerprinting, the precision of audioCtx.currentTime might get rounded depending on browser settings. In Firefox, the privacy.reduceTimerPrecision preference is enabled by default and defaults to 2ms. You can also enable privacy.resistFingerprinting, in which case the precision will be 100ms or the value of privacy.resistFingerprinting.reduceTimerPrecision.microseconds, whichever is larger.

For example, with reduced time precision, the result of audioCtx.currentTime will always be a multiple of 0.002, or a multiple of 0.1 (or privacy.resistFingerprinting.reduceTimerPrecision.microseconds) with privacy.resistFingerprinting enabled.

js
// reduced time precision (2ms) in Firefox 60
audioCtx.currentTime;
// Might be:
// 23.404
// 24.192
// 25.514
// …

// reduced time precision with `privacy.resistFingerprinting` enabled
audioCtx.currentTime;
// Might be:
// 49.8
// 50.6
// 51.7
// …

Specifications

Specification
Web Audio API
# dom-baseaudiocontext-currenttime

Browser compatibility

BCD tables only load in the browser

See also