# Options

The following table lists all available options:

Name Type Default Description
duration number 10000 Duration of the chart in milliseconds (how much time of data it will show).
ttl number Duration of the data to be kept in milliseconds. If not set, old data will be automatically deleted as it disappears off the chart.
delay number 0 Delay added to the chart in milliseconds so that upcoming values are known before lines are plotted. This makes the chart look like a continual stream rather than very jumpy on the right hand side. Specify the maximum expected delay.
refresh number 1000 Refresh interval of data in milliseconds. onRefresh callback function will be called at this interval.
onRefresh function null Callback function that will be called at a regular interval. more...
frameRate number 30 Frequency at which the chart is drawn on a display (frames per second). Decrease this value to save CPU power. more...
pause boolean false If set to true, scrolling stops. Note that onRefresh callback is called even when this is set to true.


Refer to the Configuration section if you don't know how to configure these options.

Note that the following axis options are ignored for the 'realtime' scale.

  • bounds
  • max
  • min
  • offset (always false)
  • ticks.autoSkip (always false)
  • ticks.major.enabled (always true)

# onRefresh

The onRefresh callback function takes one argument, a reference to the chart object. The this keyword for the callback function is set to the scale object.

You can update your datasets here. The chart will be automatically updated after returning, so you don't need to call chart.update(). The following example shows how to append data at every refresh interval.

const myChart = new Chart(ctx, {
  options: {
    scales: {
      x: {
        type: 'realtime',
        realtime: {
          onRefresh: function(chart) {
            chart.data.datasets.forEach(function(dataset) {
                x: Date.now(),
                y: Math.random()