Creates a new alarm for the current browser session. An alarm may fire once or multiple times. An alarm is cleared after it fires for the last time.


  name,              // optional string
  alarmInfo          // optional object


name Optional

string. A name for the alarm. Defaults to the empty string.

This can be used to refer to a particular alarm in alarms.get() and alarms.clear(). It will also be available in alarms.onAlarm as the name property of the alarms.Alarm object passed into the listener function.

Alarm names are unique within the scope of a single extension. If an alarm with an identical name exists, the existing alarm will be cleared and the alarm being created will replace it.

alarmInfo Optional

object. You can use this to specify when the alarm will initially fire, either as an absolute value (when), or as a delay from the time the alarm is set (delayInMinutes). To make the alarm recur, specify periodInMinutes.

On Chrome, unless the extension is loaded unpackaged, alarms it creates are not allowed to fire more than once per minute. If an extension tries to set delayInMinutes to a value < 1, or when to a value < 1 minute in the future, then the alarm will fire after 1 minute. If an extension tries to set periodInMinutes to a value < 1, then the alarm will fire every minute.

The alarmInfo object may contain the following properties:

when Optional

double. The time the alarm will fire first, given as milliseconds since the epoch. To get the number of milliseconds between the epoch and the current time, use If you specify when, don't specify delayInMinutes.

delayInMinutes Optional

double. The time the alarm will fire first, given as minutes from the time the alarm is set. If you specify delayInMinutes, don't specify when.

periodInMinutes Optional

double. If this is specified, the alarm will fire again every periodInMinutes after its initial firing. If you specify this value you may omit both when and delayInMinutes, and the alarm will then fire initially after periodInMinutes. If periodInMinutes is not specified, the alarm will only fire once.


Create a one-time delay-based alarm with "" for the name:

const delayInMinutes = 5;


Create a periodic delay-based alarm named "my-periodic-alarm":

const delayInMinutes = 5;
const periodInMinutes = 2;

browser.alarms.create("my-periodic-alarm", {

Create a periodic absolute alarm named "my-periodic-alarm":

const when = 1545696000;
const periodInMinutes = 2;

browser.alarms.create("my-periodic-alarm", {

Browser compatibility

BCD tables only load in the browser

Note: This API is based on Chromium's chrome.alarms API.