Chrome Version : 9.0.597.19 (Build 68937) beta & current stable I have simplified my code as far as possible. I ended up with the attached extension: content.js (content script run on every site): setInterval(function() { chrome.extension.sendRequest({ }, function(response) { //Do nothing }); }, 1); background.js (background page script): chrome.extension.onRequest.addListener(function(request, sender, sendResponse) { sendResponse({ }); }); When you install this extension, you can observe it eating up memory extremely fast (I got 90MB in 1 min with 9 tabs opened). You can speed up the process by opening more tabs. Of course, the extension I am actually developing does not send requests every millisecond, but only every 3 seconds. This just slows it down, though. A user who has run it in the background for a long time with many tabs opened has reported 100MB of memory usage, and I can reproduce it to a less extreme extent, too.