webRequest.StreamFilter.onstart
An event handler that will be called when the stream is opened and is about to begin delivering data. From this point on, the extension may use filter functions like write()
, disconnect()
, or close()
.
Browser compatibility
Report problems with this compatibility data on GitHubwebextensions-desktop | webextensions-mobile | |||||
---|---|---|---|---|---|---|
onstart | ChromeNo supportNo | EdgeNo supportNo | FirefoxFull support57 | OperaNo supportNo | SafariNo supportNo | Firefox for AndroidFull support57 |
Legend
- Full support
- Full support
- No support
- No support
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Examples
This example will replace the page content with "replacement text":
function listener(details) {
let filter = browser.webRequest.filterResponseData(details.requestId);
filter.onstart = event => {
console.log("started");
let encoder = new TextEncoder();
filter.write(encoder.encode("replacement content"));
filter.close();
}
}
browser.webRequest.onBeforeRequest.addListener(
listener,
{urls: ["https://example.org/"], types: ["main_frame"]},
["blocking"]
);