webRequest.onErrorOccurred

Fired when a request could not be processed due to an error: for example, a lack of Internet connectivity.

The error is passed to the listener as the error property of the details object.

Note that this event is not fired for HTTP errors (4XX or 5XX responses): these will go through the normal stages of a request, calling any event listeners, and setting details.statusCode to report the error.

This event is informational only.

Syntax

browser.webRequest.onErrorOccurred.addListener(function(
  details // object
) {...})
browser.webRequest.onErrorOccurred.removeListener(listener)
browser.webRequest.onErrorOccurred.hasListener(listener)

Events have three functions:

addListener(callback, filter)
Adds a listener to this event.
removeListener(listener)
Stop listening to this event. The listener argument is the listener to remove.
hasListener(listener)
Check whether listener is registered for this event. Returns true if it is listening, false otherwise.

addListener syntax

Parameters

callback

A function that will be called when this event occurs. The function will be passed the following arguments:

details
object. Details about the request. See details below.
filter
webRequest.RequestFilter. A filter that restricts the events that will be sent to this listener.

Additional objects

details

requestId
string. The ID of the request. Request IDs are unique within a browser session, so you can use them to relate different events associated with the same request.
url
string. Target of the request.
method
string. Standard HTTP method: for example, "GET" or "POST".
frameId
integer. Zero if the request happens in the main frame; a positive value is the ID of a subframe in which the request happens. If the document of a (sub-)frame is loaded (type is main_frame or sub_frame), frameId indicates the ID of this frame, not the ID of the outer frame. Frame IDs are unique within a tab.
parentFrameId
integer. ID of the frame that contains the frame which sent the request. Set to -1 if no parent frame exists.
tabId
integer. The ID of the tab in which the request takes place. Set to -1 if the request isn't related to a tab.
type
webRequest.ResourceType. The type of resource being requested: for example, "image", "script", "stylesheet".
timeStamp
number. The time when this event fired, in milliseconds since the epoch.
ipOptional
string. The server IP address that the request was actually sent to. Note that it may be a literal IPv6 address.
fromCache
boolean. Indicates if this response was fetched from disk cache.
error
string. The error description. This string is an internal error string, may vary from one browser to another, and is not guaranteed to stay the same between releases.

Browser compatibility

EdgeFirefoxChromeOpera
Basic support?45.0Yes33
Firefox
Basic support48.0

Examples

var target = "<all_urls>";

/*
e.g., with no network:
"https://developer.mozilla.org/en-US/"
NS_ERROR_NET_ON_RESOLVED in Firefox
net::ERR_INTERNET_DISCONNECTED in Chrome
*/
function logError(responseDetails) {
  console.log(responseDetails.url);
  console.log(responseDetails.error);
}

chrome.webRequest.onErrorOccurred.addListener(
  logError,
  {urls: [target]}
);

Acknowledgements

This API is based on Chromium's chrome.webRequest API. This documentation is derived from web_request.json in the Chromium code.

Document Tags and Contributors

 Contributors to this page: wbamberg
 Last updated by: wbamberg,