Why won’t my Safari browser open

macOS

1. Update Safari, if an update is available. Update may come with bug fixes.

    Update to the latest version of Safari - Apple Support

    Update macOS on Mac - Apple Support

2. Force Quit Safari, launch Safari holding the Shift key down.

    About pop-up ads and windows in Safari - Apple Support

3. Startup in Safe Mode. 

   Start up your Mac in safe mode - Apple Support.  

    Quote:

    It also does a basic check of your startup disk, similar to using First Aid in Disk Utility. 

    And it deletes some system caches, including font caches and 

    the kernel cache, which are automatically created again as needed.

4. Clear History

    Clear your browsing history in Safari on Mac - Apple Support

    Please read the article before clearing history, 

    this is like a low level resetting of Safari without affecting passwords and bookmarks.

5. If Safari doesn't open a webpage or isn’t working as expected

    If Safari on Mac doesn't open a webpage or isn’t working as expected - Apple Support

6. If these steps  don’t help, download EtreCheck, run it to see if there is any adware installed or not.

      https://etrecheck.com

      Click  “Free download” button,

      Open Downloads folder, click on it to open, and then select ”Open”.

      “Choose a problem” from the popup menu box, and then “Start EtreCheck” in the dialog.

      Click “Share Report” button in the toolbar, select “Copy report” .

      Paste the report when you reply.