Downloading from YouTube without cookies doesn't work anymore

[sikthehedgehog]

Checklist

• I'm reporting a broken site support issue
• I've verified that I'm running youtube-dl version 2020.09.14
• I've checked that all provided URLs are alive and playable in a browser
• I've checked that all URLs and arguments with special characters are properly quoted or escaped
• I've searched the bugtracker for similar bug reports including closed ones
• I've read bugs section in FAQ

Verbose log

[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'-v', u'-f', u'18', u'https://www.youtube.com/watch?v=6haepsZSMsg']
[debug] Encodings: locale UTF-8, fs UTF-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2020.09.14
[debug] Python version 2.7.17 (CPython) - Linux-4.15.0-117-generic-x86_64-with-Ubuntu-18.04-bionic
[debug] exe versions: ffmpeg 4.1.3-0ppa1, ffprobe 4.1.3-0ppa1, phantomjs 2.1.1, rtmpdump 2.4
[debug] Proxy map: {}
[youtube] 6haepsZSMsg: Downloading webpage
ERROR: Unable to download webpage: HTTP Error 429: Too Many Requests (caused by HTTPError()); please report this issue on https://yt-dl.org/bug . Make sure you are using the latest version; type  youtube-dl -U  to update. Be sure to call youtube-dl with the --verbose flag and include its complete output.
  File "/usr/local/bin/youtube-dl/youtube_dl/extractor/common.py", line 627, in _request_webpage
    return self._downloader.urlopen(url_or_request)
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 2238, in urlopen
    return self._opener.open(req, timeout=self._socket_timeout)
  File "/usr/lib/python2.7/urllib2.py", line 435, in open
    response = meth(req, response)
  File "/usr/lib/python2.7/urllib2.py", line 548, in http_response
    'http', request, response, code, msg, hdrs)
  File "/usr/lib/python2.7/urllib2.py", line 473, in error
    return self._call_chain(*args)
  File "/usr/lib/python2.7/urllib2.py", line 407, in _call_chain
    result = func(*args)
  File "/usr/lib/python2.7/urllib2.py", line 556, in http_error_default
    raise HTTPError(req.get_full_url(), code, msg, hdrs, fp)

Description

What the verbose log above says. In particular this:

youtube-dl -f 18 https://www.youtube.com/watch?v=6haepsZSMsg

[youtube] 6haepsZSMsg: Downloading webpage
ERROR: Unable to download webpage: HTTP Error 429: Too Many Requests (caused by HTTPError()); please report this issue on https://yt-dl.org/bug . Make sure you are using the latest version; type  youtube-dl -U  to update. Be sure to call youtube-dl with the --verbose flag and include its complete output.

But this works:

youtube-dl --cookies cookies.txt -f 18 https://www.youtube.com/watch?v=6haepsZSMsg

[youtube] 6haepsZSMsg: Downloading webpage
[youtube] 6haepsZSMsg: Downloading MPD manifest
[download] Destination: Zeta Wing C64-6haepsZSMsg.mp4
[download] 100% of 6.32MiB in 00:05

…I was going to report this as a bug until at last minute before sending submit I decided to try with cookies. I guess that using cookies is mandatory now? (disclaimer: I only tried with the cookies from my logged in tab, I haven't checked to see if cookies from not logged in tabs work too)