Steps to close all open tabs on your Safari browser all at once:

• If there are any tabs you wish to keep open, you'll have to close them one at a time - or you can make a note of them and reopen them later - but if you want to close them all at once,
• On your iPhone, open the Safari app.
• 
  
• In the lower right corner, press and hold the squares.
• 'Close All [x] Tabs' should be selected.
• 'Verify'
• All [x] tabs should be closed.

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