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This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

The SyncEvent() constructor creates a new SyncEvent object.


var mySyncEvent = new SyncEvent(type, init)


The type of the Event.
init Optional
An options object containing any custom settings that you want to apply to the event object. Options are as follows:
  • tag: A developer-defined unique identifier for this SyncEvent.
  • lastChance: A Boolean indicating that the user agent will not make further synchronization attempts after the current attempt.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support49 ? ? ? ? ?
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support No49 ? ? ? ? ?

Document Tags and Contributors

 Contributors to this page: fscholz, rolfedh, jpmedley
 Last updated by: fscholz,