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(
  listener,             // function
  filter                //  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

documentUrl
string. URL of the document in which the resource will be loaded. For example, if the web page at "https://example.com" contains an image or an iframe, then the documentUrl for the image or iframe will be "https://example.com". For a top-level document, documentUrl is undefined.
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.
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.
fromCache
boolean. Indicates if this response was fetched from disk cache.
ipOptional
string. The server IP address that the request was actually sent to. Note that it may be a literal IPv6 address.
method
string. Standard HTTP method: for example, "GET" or "POST".
originUrl

string. URL of the resource which triggered the request. For example, if "https://example.com" contains a link, and the user clicks the link, then the originUrl for the resulting request is "https://example.com".

The originUrl is often but not always the same as the documentUrl. For example, if a page contains an iframe, and the iframe contains a link that loads a new document into the iframe, then the documentUrl for the resulting request will be the iframe's parent document, but the originUrl will be the URL of the document in the iframe that contained the link.

parentFrameId
integer. ID of the frame that contains the frame which sent the request. Set to -1 if no parent frame exists.
proxyInfo

object. This property is present only if the request is being proxied. It contains the following properties:

host
string. The hostname of the proxy server.
port
integer. The port number of the proxy server.
type

string. The type of proxy server. One of:

  • "http": HTTP proxy (or SSL CONNECT for HTTPS)
  • "https": HTTP proxying over TLS connection to proxy
  • "socks": SOCKS v5 proxy
  • "socks4": SOCKS v4 proxy
  • "direct": no proxy
  • "unknown": unknown proxy
username
string. Username for the proxy service.
proxyDNS
boolean. True if the proxy will perform domain name resolution based on the hostname supplied, meaning that the client should not do its own DNS lookup.
failoverTimeout
integer. Failover timeout in seconds. If the proxy connection fails, the proxy will not be used again for this period.
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.
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.
timeStamp
number. The time when this event fired, in milliseconds since the epoch.
type
webRequest.ResourceType. The type of resource being requested: for example, "image", "script", "stylesheet".
url
string. Target of the request.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxOperaFirefox for Android
Basic supportChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesFirefox Android Full support 48
details.documentUrlChrome No support NoEdge No support NoFirefox Full support 54Opera No support NoFirefox Android Full support 54
details.errorChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesFirefox Android Full support 48
details.frameIdChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesFirefox Android Full support 48
details.fromCacheChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesFirefox Android Full support 48
details.ipChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesFirefox Android Full support 48
details.methodChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesFirefox Android Full support 48
details.originUrlChrome No support NoEdge No support NoFirefox Full support 48Opera No support NoFirefox Android Full support 48
details.parentFrameIdChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesFirefox Android Full support 48
details.proxyInfoChrome No support NoEdge No support NoFirefox Full support 57Opera No support NoFirefox Android Full support 57
details.requestIdChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesFirefox Android Full support 48
details.tabIdChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesFirefox Android Full support 48
details.timeStampChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesFirefox Android Full support 48
details.typeChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesFirefox Android Full support 48
details.urlChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesFirefox Android Full support 48

Legend

Full support  
Full support
No support  
No support

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);
}

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

Example extensions

Acknowledgements

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

Microsoft Edge compatibility data is supplied by Microsoft Corporation and is included here under the Creative Commons Attribution 3.0 United States License.

Document Tags and Contributors

Contributors to this page: hellosct1, wbamberg, em_te, Makyen
Last updated by: hellosct1,