import Innertube from 'youtubei.js';

const yt = await new Innertube();

// Downloading videos returns a Node Stream which you can consume
const stream = yt.download('VIDEO_ID');

// Alternatively, you may want more info before downloading
const info = await yt.getInfo('VIDEO_ID');

// Then you may request a download stream
const stream_from_info = yt.download();

Download Methods

There are two options for downloading a video:

Innertube.download(video_id: string, options?: DownloadOptions)
VideoInfo.download(options?: DownloadOptions)

The download methods are identical, but the first one is a convenience method for the second one.

Download Options

The DownloadOptions object is used to choose the format for download

format: The format of the video to download. Use 'any' to pick any format available. (default: 'mp4')
quality: The quality of the video to download. (default: '360p') There's some options:
- 'best': The best quality available. Picks the highest dimensions and highest bitrate stream.
- 'bestefficiency': The best quality available. Picks the highest dimensions and lowest bitrate stream.
- You may also filter via quality labels such as '720p' or '1080p'.
type: The type of the video to download. (default: 'videoandaudio')
- 'videoandaudio': Download both video and audio.
- 'video': Download only video.
- 'audio': Download only audio.
range: The range of the video to download. (default: undefined)
- range.start: First byte to download.
- range.end: Last byte to download.

Download Events

In addition to the normal events emitted by Node Streams, YouTube.js also emits the following events on the stream:

info: Emitted when the video metadata is available. (only emiited with Innertube.download not with VideoInfo.download)
progress: Emitted when the video is downloading.
start: Emitted when the video starts downloading.

stream.on('info', (info) => {
  // `info` is an instance of VideoDetails as returned by Innertube.getBasicInfo() and is thus not complete with all the details.
});

stream.on('progress', (progress) => {
    // The progress object has the following properties
    // progress.size - size of the video in megabytes as string
    // progress.percent - percentage of the video downloaded as string
    // progress.chunk_size - size of the last chunk downloaded as bytes
    // progress.downloaded_size - size of the video downloaded in megabytes as string
    // progress.raw_data.chunk_size - size of the last chunk downloaded as bytes
    // progress.raw_data.downloaded_size - size of the video downloaded as bytes
    // progress.raw_data.size - size of the response range in bytes
});

stream.on('start', () => {
    // start does not have any data
});

Aborting Downloads

The download stream may be aborted by calling stream.cancel()