Authenticated access on Youtube
In case you get an error saying for example
This video may be inappropriate for some users this means it is restricted from unauthorized access. The same would be if you open it in browser's private mode.
To get access to it in the browser you normally must authenticate yourself (i.e. log in to Youtube) so Youtube can check your identity and authorize you (i.e. give access) for viewing this video if you, say, 18 or older.
Youtube provides authentication possibility for third-party software, however filter does not use this way since it anyway would not be allowed by Youtube. An other way is used instead: authentication can be "simulated" by borrowing browser cookies from Youtube.
Once again in other words. Doing this you give the filter ability to pretend it is you so Youtube can give an access to the videos that you are able to access in the browser. Which means first: it won't give possibility to access anything that you do not have access to in the browser. Second: it (probably) gives the filter possibility to act on behalf of given Youtube account. Although filter won't do anything bad, you are informed now and are free to choose to ignore such trick if you are not comfortable with this knowledge.
Now to the point. The following instructions are designed for Firefox and Chrome but in other browsers it should be possible similar way.
Log in to Youtube if you have not done this yet. Then open this URL: https://www.youtube.com/favicon.ico. Actually you can use any Youtube page but with single image it will be easier to follow next steps.
Open Web Developer Tools (this can be done by pressing
Ctrl+Shift+I) and select
Network tab there.
F5 to reload image. This will cause its URL to appear in
Network tab. Right click on it and select
Copy Copy as cURL. There are two such commands in each browser (see screenshots) but in this case it does not really matter which command to use.
Now need to set these cookies in the filter.
Go to preferences
Network HTTP Enable persistent cookie storage Storage Modify. Cookie editor will appear. Press
Paste button there. In appeared window leave everything as is and just press
OK button. Now press
OK button in cookie editor to apply these modifications.
Support in youtube-dl
For some videos youtube-dl may be able to bypass authorization. So you may check first if authentication is actually required.
Unlike the way used in filter, in youtube-dl you have to supply your username and password.
How to perform authentication in youtube-dl you can read in its documentation: Authentication with .netrc file.
Help Troubleshooting Authenticated download