Note you must have the tabs
permission set in your manifest file
"permissions": [
"tabs"
],
http://developer.chrome.com/extensions/tabs.html
or the activeTab
permission if initiated by a click on the extension button[Xan]
https://developer.chrome.com/extensions/activeTab
Code:
chrome.tabs.query({currentWindow: true, active: true}, function(tabs){
console.log(tabs[0].url);
});