Google Webmaster Tools added support for new website verification method, called Google Tag Manager as announced in WMT Blog.

This option is visible in “Alternate Methods” at bottom when you try to add new site and on verification page, shown as following:

Google Tag Manager  Use your Google Tag Manager account.

The Google Tag Manager container ID is used only to verify site ownership. No Google Tag Manager data will be accessed.

If you are new to Google Tag Manager, than i will let you know that you can use Google Tag Manager without much knowledge of coding etc. It lets you add and update your website tags very easily and for free and whenever you need.