how to block web sites from storing data

Take cursor on top menu bar > History > clear all history and website data , your old browsed history and cookies will be deleted .

In safari preferences > privacy > cookies and website data > check the box of always from websites I list .

An article to be read : Safari for Mac: Manage cookies and website data using Safari

In normal browsing some cookies will always be stored if you browse a website , but you can delete them frequently .

And in your headlines question :

how to block web sites from storing data

If you feel sometimes can use private browsing : Safari for Mac: Use Private Browsing windows in Safari

Some users also use this method > click on manage website & select the the desired ones and click on remove .

And you can check the box websites use of location services deny without prompting & ask websites not to track me .

Read these articles also : About Location Services in OS X and Safari - Apple Support

: macOS Sierra: Manage which apps can use Location Services

Regards ,

Appreciate your both links and there is no harm in posting etrecheck report and if user feel Malware Bytes is also an good option to scan the malware , by checking the options posted in the above screen shot one can partially hide their location , but private browsing mode disables cookies and browsing history will not be saved .

If we open security & privacy > privacy > Enable location services is checked and I have checked the box of ask websites not to track me in safari preferences still there is an arrow head in front of calendar app & calendar app box is unchecked , and this arrow head will vanish after 24 hours .

Because some websites have different techniques to find the location of the user .

Regards ,

Using Safari's "Manage Website Data..." followed by "Remove All" does not remove databases created by websites. To remove them please refer to the following Discussion: How to delete "database" Cookie?

Repeated here for reference,

John Galt wrote:

Those files are stored in

~/Library/Safari/Databases

Navigate to that folder and drag its contents to the Trash.

Those Databases will return upon loading the websites that create them.

This is not abnormal behavior and there is no reason to suspect malware is the cause. If removing the folder contents described above solves the problem then no other action is justified.

I, and the vast majority of the people who post here, are not Apple employees, but users like you who volunteer our time to try to help people. You are not our customer. If you want to say something to Apple, send feedback.

Feedback

Same problem as you with eBay and Face Book even though I have never signed up. This is just another display of big corporations spying on the masses. This actually seems like something Apple producers support or else they would help stop this wrongful invasion privacy. If anyone has knowledge of how to stop this please help us so we might help others.

As the 2nd article points out, they are capable of regenerating after deletion with files that go to many parts of the system.

Safari/Browsers – can’t delete cookies

Evercookie

The myth of the dangerous cookie

Quit Safari.

In Finder go to Go menu and then Go to Folder.

Copy and paste this ~/Library/Safari/Databases.

Delete the contents of the folder.

Launch Safari again and check if all is ok.

If that doesn’t work, copy and paste this ~/Library/Safari/LocalStorage.

Delete the contents of the folder.

Then go to Safari/History and delete any entries for the related websites.

Test.

Just like the others have stated that doesn’t work I’ve tried all of those suggestions, so what is the problem? You’re the supposed to be Geniuses are you not, so why not fix this problem? Figure it out because we are your customers and this is your technology you of all should have fixed this problem by now.

Have you tried a "Private Browsing" window?

<Safari for Mac: Use Private Browsing windows in Safari>

FWIW, you may have adware/malware installed. You can check with either of these two programs.

https://www.malwarebytes.com/mac/

http://etrecheck.com/

welcome. When I first read your post I thought you were getting pop-ups. As John mentioned there's no reason to suspect malware otherwise.