Chrome extension asks if you sure wanna get distracted on specific domains.

You can install the latest version from the Chrome Web Store.

• Go to chrome:https://extensions
• Turn Developer mode on
• Click Load unpacked and load app folder

In the extension's settings you can write multiple lines with simple globs to include or exclude different urls.
Examples:

• *github.com* to include urls containing github.com
• -*github.com/magnickolas* to exclude urls containing github.com/magnickolas

Iamsure will ask you on a webpage with a matching url when it loads — whether to stay on it or close the tab.