downloads.download()

The download() function of the {{WebExtAPIRef("downloads")}} API downloads a file, given its URL and other optional preferences.

If the URL uses the HTTP or HTTPS protocol, the request includes all the relevant cookies, that is, those cookies set for the URL's hostname, secure flag, path, and so on. The default cookies, the cookies from the normal browsing session, are used unless:

• the incognito option is used, then the private browsing cookies are used.
• the cookieStoreId option is used, then the cookies from the specified store are used.

If both filename and saveAs are specified, the Save As dialog is displayed, populated with the filename.

This is an asynchronous function that returns a Promise.

Syntax

let downloading = browser.downloads.download(
  options                   // object
)

Parameters

• options
  • : An object specifying what file you wish to download, and any other preferences you wish to set concerning the download. It can contain the following properties:

    • allowHttpErrors {{optional_inline}}

      • : A boolean flag that enables downloads to continue even if they encounter HTTP errors. Using this flag, for example, enables the download of server error pages. Default value false. When set to:
        • false, the download is canceled when it encounters an HTTP error.
        • true, the download continues when an HTTP error is encountered and the HTTP server error is not reported. However, if the download fails due to file-related, network-related, user-related, or other error, that error is reported.

    • body {{optional_inline}}

      • : A string representing the post body of the request.

    • conflictAction {{optional_inline}}

      • : A string representing the action you want taken if there is a filename conflict, as defined in the {{WebExtAPIRef('downloads.FilenameConflictAction')}} type (defaults to "uniquify" when it is not specified).

    • cookieStoreId {{optional_inline}}

      • : The cookie store ID of the contextual identity the download is associated with. If omitted, the default cookie store is used. Use requires the "cookies" API permission. See Work with contextual identities for more information.

    • filename {{optional_inline}}

      • : A string representing a file path relative to the default downloads directory — this provides the location where you want the file to be saved, and what filename you want to use. Absolute paths, empty paths, path components that start and/or end with a dot (.), and paths containing back-references (../) will cause an error. If omitted, this value will default to the filename already given to the download file, and a location immediately inside the downloads directory.

    • headers {{optional_inline}}

      • : If the URL uses the HTTP or HTTPS protocols, an array of objects representing additional HTTP headers to send with the request. Each header is represented as a dictionary object containing the keys name and either value or binaryValue. The headers that are forbidden by XMLHttpRequest and fetch cannot be specified, however, Firefox 70 and later enables the use of the Referer header. Attempting to use a forbidden header throws an error.

    • incognito {{optional_inline}}

      • : A boolean: if present and set to true, then associate this download with a private browsing session. This means that it will only appear in the download manager for any private windows that are currently open.

    • method {{optional_inline}}

      • : A string representing the HTTP method to use if the url uses the HTTP[S] protocol. This may be either "GET" or "POST".

    • saveAs {{optional_inline}}

      • : A boolean that specifies whether to provide a file chooser dialog to allow the user to select a filename (true), or not (false).

        If this option is omitted, the browser will show the file chooser or not based on the general user preference for this behavior (in Firefox this preference is labeled "Always ask you where to save files" in about:preferences, or browser.download.useDownloadDir in about:config).

        [!NOTE] Firefox for Android raises an error if saveAs is set to true. The parameter is ignored when saveAs is false or not included.

    • url

      • : A string representing the URL to download.

Return value

A Promise. If the download started successfully, the promise will be fulfilled with the id of the new {{WebExtAPIRef("downloads.DownloadItem")}}. Otherwise, the promise will be rejected with an error message taken from {{WebExtAPIRef("downloads.InterruptReason")}}.

If you use URL.createObjectURL() to download data created in JavaScript and you want to revoke the object URL (with revokeObjectURL) later (as it is strongly recommended), you need to do that after the download has been completed. To do so, listen to the downloads.onChanged event.

Examples

The following snippet attempts to download an example file, also specifying a filename and location to save it in, and uniquify as the value of the conflictAction option.

function onStartedDownload(id) {
  console.log(`Started downloading: ${id}`);
}

function onFailed(error) {
  console.log(`Download failed: ${error}`);
}

let downloadUrl = "https://example.org/image.png";

let downloading = browser.downloads.download({
  url: downloadUrl,
  filename: "my-image-again.png",
  conflictAction: "uniquify",
});

downloading.then(onStartedDownload, onFailed);

{{WebExtExamples}}

Browser compatibility

{{Compat}}

[!NOTE] This API is based on Chromium's chrome.downloads API.