1. download extension cookie.txt
Firefox extension
https://addons.mozilla.org/en-US/firefox/addon/cookies-txt/
2. Login in youtube
3. Click cookie.txt icon > current site
4. Save and put it in the folder where you install or extract. Default name cookies.undefined.txt is used in the following steps.
5. Open youtube-dlg
6. Click the gear > option > extra
7. Paste following codes and replaced by your own content in the command line option.
-u yourusername -p yourpasssword --cookie cookies.undefined.txt
8. Start your download.
9. Restart maybe required if download still result a error.
Chrome extension
https://chrome.google.com/webstore/detail/cookiestxt/njabckikapfpffapmjgojcnbfjonfjfg
2. Login in youtube
3. Click cookie.txt icon > download this tab
4. Save and put it in the folder where you install or extract. Default name cookies.txt is used in the following steps.
5. Open youtube-dlg
6. Click the gear > option > extra
7. Paste following codes and replaced by your own content in the command line option.
-u yourusername -p yourpasssword --cookie cookies.txt
8. Start your download.
9. Restart maybe required if download still result a error.
Hope this help.