This article explains how to close all your Safari tabs at once.These directions work for iOS 12 and up, including iPadOS.
Use the Tabmenu to close all open tabs simultaneously.
Tap and hold theTab button, which looks like two stacked squares.
TapClose All [#] Tabs.
Tap the same button once more to confirm.This will close all tabs immediately.
The Tab menu is also how you launch a private browsing session.
Another way to close all tabs on iPhone or iPad is through the Settings app. This is helpful if you can't close the tabs within Safari, like if the browser won't open.
When you clear all tabs this way, you're also erasing the Safari cache, which includes your browsing history, cookies, and other browsing data. That means you'll need to log back into any websites that normally log in automatically when you visit them.
Open the Settings app and tapSafari.
Scroll down and chooseClear History and Website Data>Clear.
To close all tabs at the same time, chooseClose Tabs.