There are cases in which Google Search Console, Magento Security Tool or any other service ask to verify you to be the owner of the site and confirm it by adding to the Page <head> tag a code. In order to easily add it in the Magento 2 please go to Admin Panel > Content > Configuration.
Then, choose the store view you want the head tag to be changed on or select Global in order to change it on every store views.
Afterwards, find the HTML Head section and add your code in the Scripts and Style Sheets field.
Once the changes have been performed don't forget to press the Save Configuration button and flush Magento cache.