How can I get the current tab URL for chrome extension?

Just an FYI for people from Google:

The method OP uses is deprecated. To get the tab the user is viewing and only in the window they are viewing use this:

  chrome.tabs.query({active: true, currentWindow: true}, function(tabs) {

     // since only one tab should be active and in the current window at once
     // the return variable should only have one entry
     var activeTab = tabs[0];
     var activeTabId = activeTab.id; // or do whatever you need

  });