Safari issues 10.13.3

Go step by step and test.

1. Click  in the menu bar and choose “Force Quit”.

If Safari shows up on the list, select it, and then click “Force Quit” button.

Hold the shift key down and launch Safari.

2. If Safari is slow, stops responding, quits unexpectedly, or has other issues

https://support.apple.com/en-us/HT203353

Safari > Preferences > Extensions

Select and turn off all extensions.

Section: Manage Extensions

https://support.apple.com/guide/safari/use-safari-extensions-sfri32508/mac

3. If you can’t open a website in Safari

https://support.apple.com/guide/safari/if-you-cant-open-a-website-in-safari-ibrw 1071/mac

4. Safari > Preferences > Advanced > Accessibility:

Uncheck the box beside “Never use font sizes smaller than”.

5. Delete com.apple.Safari.plist file and test.

Empty the Trash.

Quit all applications.

Hold the option key down and click the "Go" menu in the Finder menu bar.

Select "Library" from the drop down.

Library > Preferences > com.apple.Safari.plist

Right click on it and select "Move it to Trash".

Restart and relaunch Safari holding the shift key down.

If this doesn’t help, “Put Back” the com.apple.Safari.plist

Right click on the Trash icon in the Dock and select “Open”.

Right click on the com.apple.Safari.plist and select “Put Back”.

Select ”Replace” from the dialog when it appears.

Try setting up another admin user account to see if the same problem continues. If Back-to-My Mac is selected in System Preferences, the Guest account will not work. The intent is to see if it is specific to one account or a system wide problem. This account can be deleted later. Please post if this worked or not.

Isolating an issue by using another user account

If the problem is still there, try booting into the Safe Mode using your normal account. Disconnect all peripherals except those needed for the test. Shut down the computer and then power it back up after waiting 10 seconds. Immediately after hearing the startup chime, hold down the shift key and continue to hold it until the gray Apple icon and a progress bar appear. The boot up is significantly slower than normal. This will reset some caches, forces a directory check, and disables all startup and login items, among other things. When you reboot normally, the initial reboot may be slower than normal. If the system operates normally, there may be 3rd party applications which are causing a problem. Try deleting/disabling the third party applications after a restart by using the application un-installer or by using the developer’s uninstall instructions. For each disable/delete, you will need to restart if you don't do them all at once. Please post if this worked or not.

Safe Mode - About El Capitan
also Sierra

Safe Mode Startup – El Capitan. also Sierra

If it works in the Safe Mode, try running this program when booted normally and then copy and paste the output in a reply. The program was created by Etresoft, a frequent contributor. Please use copy and paste as screen shots can be hard to read. Click “Share Report” button in the toolbar, select “Copy to Clipboard” and then paste into a reply. This will show what is running on your computer. No personal information is shown. You can run the report for free at least once, but if you run it several times, at some point it will ask you to pay a license fee.

Etrecheck – System Information

Thanks for the feedback. It might help others.