How to download only subtitles of videos using youtube-dl

There is an option, clearly mentioned in the documention:

Subtitle Options:

--write-sub                      Write subtitle file
--write-auto-sub                 Write automatic subtitle file (YouTube only)
--all-subs                       Download all the available subtitles of the video
--list-subs                      List all available subtitles for the video
--sub-format FORMAT              Subtitle format, accepts formats preference, for example: "srt" or "ass/srt/best"
--sub-lang LANGS                 Languages of the subtitles to download (optional) separated by commas, use IETF language tags like 'en,pt'

So for example, to list all subs for a video:

youtube-dl --list-subs https://www.youtube.com/watch?v=Ye8mB6VsUHw

To download all subs, but not the video:

youtube-dl --all-subs --skip-download https://www.youtube.com/watch?v=Ye8mB6VsUHw

Or you can only download one subtitle

youtube-dl --write-sub --sub-lang en --skip-download URL 

Another simple way to download subtitles from YouTube is to download Google2SRT. Google2SRT is a free, open source program for Windows, Mac and Linux that is able to download, save and convert multiple subtitles from YouTube videos.

Usage

^{Click the links to see screenshots of steps 1 and 2.}

1. Paste the URL in the Google subtitles text box and click Read.

2. Choose the language by selecting the appropriate check box provided and press Go.

3. View the destination folder that was input in the SRT subtitles textbox to locate the SRT files.