You can’t lock a tab in Google Chrome, there isn’t an option for this. Some users want this feature as any tab can be closed accidentally by dragging, which opens as a new window or they want to remember particular tabs like Facebook, Twitter, YouTube when too many tabs are open. As extensions add features to the browsers, Lock Tab is an extension for Chrome that allows to lock tabs to prevent from accidental closing.

Prevent accidental closing of tabs in Chrome by locking them with Lock Tab

After installing the Lock Tab extension, a lock icon appears on Chrome’s address bar – it appears in grey color on New Tab Page and turns to blue for any tab that has any page open.

Visit extension options and make the keyboard combination as Ctrl+Alt+L.

Note: You may need to restart the Chrome for the extension icon to active for already open tabs.

Now navigate to the tab/page you want to lock and click on the blue-colored lock icon or use the keyboard shortcut Ctrl +Alt + L instead.

The locked tab appears with a tab title “Locked:tab_title”. You can toggle locking and unlocking of tabs by clicking on the lock icon.

When you try to close a locked tab, you’ll be alerted with a dialog: ‘ do you want to leave this site’, clicking ‘Leave’ will close the tab, clicking ‘Stay’ or taking no action makes the tab to remain open.

This extension does have its limitations: you can’t lock special pages like Gmail, Chrome new tab page, Chrome extension page, where the lock icon appears in grey color as it can’t act on those pages.

Lock Tab extension in Chrome Web Store