webNavigation.onBeforeNavigate

browser.webNavigation.onBeforeNavigate.addListener(
  listener,                   // function
  filter                      // optional object
)
browser.webNavigation.onBeforeNavigate.removeListener(listener)
browser.webNavigation.onBeforeNavigate.hasListener(listener)

Events have three functions:

addListener(listener)

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.

listener

The function called when this event occurs. The function is passed this argument:

details

object. Details about the navigation event. See the details section for more information.

filter Optional

object. An object containing a single property url, which is an Array of events.UrlFilter objects. If you include this parameter, then the event fires only for transitions to URLs which match at least one UrlFilter in the array. If you omit this parameter, the event fires for all transitions.

tabId

integer. The ID of the tab in which the navigation is about to occur.

url

string. The URL to which the given frame will navigate.

processId

integer. The ID of the process in which this tab is being rendered (This property is not supported on Firefox, and it is deprecated on Chrome).

frameId

integer. Frame in which the navigation is about to occur. 0 indicates that navigation happens in the tab's top-level browsing context, not in a nested <iframe>. A positive value indicates that navigation happens in a nested iframe. Frame IDs are unique for a given tab and process.

parentFrameId

integer. ID of this frame's parent. Set to -1 if this is a top-level frame.

timeStamp

number. The time when the browser is about to start the navigation, in milliseconds since the epoch.

Logs the target URLs for onBeforeNavigate, if the target's hostname contains "example.com" or starts with "developer".

const filter = {
  url:
  [
    {hostContains: "example.com"},
    {hostPrefix: "developer"}
  ]
}

function logOnBefore(details) {
  console.log(`onBeforeNavigate to: ${details.url}`);
}

browser.webNavigation.onBeforeNavigate.addListener(logOnBefore, filter);