Safari new popup window problem

In Safari - Preferences - Websites - Reader : Select & remove or modify any shown sites, then change 'when visiting other sites' to Off if that is your preference.

The darker (meaning active) Reader icon just to the left of the web address shows that.

Safari Websites preferences - Apple Support

Enter in user library macOS Sierra: Library folder

Find folders Caches , Cookies , Saved application State , Safari ( select all contents use command and A ) , delete them ( command and delete button on the keyboard ) to the trash .

Find folder Preferences > drag and drop com.apple.safari.plist to the trash , restart the machine and empty the trash , you have to once again set the home page an article for it Set your homepage - Apple Support

Also read some articles If Safari is slow, stops responding, quits unexpectedly, or has other issues - Apple Support

Make a good practice of deleting all history and website data .

Verify is the issue persisting in new user account also an article for it How to test an issue in another user account on your Mac - Apple Support

And , avoid using third party add ons , cleaners , anti virus in Mac .

Lastly running SMC , safe mode , NVRAM / PRAM are also to be considered and can be applied .

🙂 Thanks !

Remove caches , cookies contents from user library after a month or two , these are temp files accumulating , restart the Mac and empty the trash , Mac users avoid deleting them and that has to be done .

In your case the data was also stored in saved application state deleting the contents helped .

The last option was resetting safari in very rare case " entire safari folder " contents from user library are removed and the plist for safari that was mentioned .

These are the basic tricks to resolve safari corruptions .

Safari has inbuilt feature to create new contents immediately , also sometimes deleting the complete " safari folder " from the user library is done but that is also very rare and is performed according to situation , not occasionally .

Restarting the Mac and emptying the trash creates new safari folder .

I hope you have not installed anti-virus software. That can make things much worse. Posting a snapshot of your configuration can ofter allow us to quickly resolve a problem. Fortunately there is a safe and secure way to do that.

A respected and long-serving member of these communities has created a simple utility that will take that "snapshot" of your configuration without revealing any sensitive information about you and your computer. It does not run in the background and therefore creates no performance penalties. It is Etrecheck, and is available here:

http://etrecheck.com/

Run it and, when its report displays, click Etrecheck's "Share Report" icon and then "Copy Report" from the resulting dropdown. Paste the entire report into a response to your own thread here. It will often allow us to quickly identify or eliminate software as the problem.

Is this totally random or associated with certain web sites? Not the same thing, but see if the answer inn this post helps.

Safari – loading pages in wrong tab See 12 Mar post by ravivo2001

Does it still look like your screenshot ?. If so, that appears exactly as Safari's 'Reader' feature, suggested previously.