Browser extensions are useful, but they can increase your browser’s memory consumption, make it take longer to open, and slow it down in general. But how do you measure the impact a browser extension has on your system?

Each browser offers its own ways to pin down an extension’s memory consumption, CPU usage, or startup delay. The exact information you’ll get depends on your browser.

Mozilla Firefox

Mozilla Firefox doesn’t offer an easy way to view a browser extension’s memory usage. Rather than digging this information up yourself, you can use a Firefox extension that will display this information for you. Yes, it may seem silly that you’re installing yet another browser extension to see how much extensions are slowing down your browser, but you can always uninstall or disable this extension after using it.

To do this, install the about:addons-memory extension and open the about:addons-memory page in a Firefox tab. You’ll see a list of the extensions you have installed, sorted by how much memory they use. This will give you a better idea of how much memory your add-ons use and which you may benefit from disabling. If you have an add-on with a memory leak, it may continue to use more and more memory the longer your browser runs — you can check this page later to see if any add-ons are consuming a large amount of memory.

Google Chrome

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Google Chrome is a multi-process browser and many browser extensions run as their own process. This means that you can use Chrome’s integrated Task Manager to view the memory consumption — and even current CPU usage — of your running browser extensions. The Task manager will also display the resources used by your installed Chrome web apps as well as each open browser tab and other background processes.

To open the Task Manager, click Chrome’s menu button, point to Tools, and select Task Manager. You can also press Ctrl + Escape to quickly open the task manager.

The Task Manager will give you an idea of how heavy each extension is. Bear in mind that only extensions that run in the background are listed here, so extensions that inject code into pages you load may not appear in the list, although they may have an impact on page loading times.

Internet Explorer

Internet Explorer doesn’t expose the memory used by individual browser add-ons. However, it does give you information about how long each browser add-on takes to load. From this, you can get an idea of how heavy a browser add-on is — if it takes longer to load, it may be consuming more memory as well as slowing things down.

To find this information, click the gear menu in Internet Explorer and select Manage Add-ons. You’ll see each browser extension’s load time listed under the Load time column — to prevent an add-on from loading along with IE, select it in the list and click the Disable button.

Internet Explorer also displays “Navigation time” for each add-on – – that’s how much of a delay an add-on adds each time you navigate to, or load, a new web page.

Use Your Browser’s Safe Mode

Actually determining how much system resources a particular browser extension uses is a difficult problem. The above tricks allow you to get at the information browsers give you, but this information doesn’t provide a complete picture.

Fortunately, there is a way to see how your browser performs without any add-ons at all. To do this, open your browser in “safe mode,” where it will load without any extensions at all. If your browser appears noticeably speedier in this mode, you’ll know that certain add-ons are bogging it down. Then, it would just be a matter of disabling add-ons one-by-one in normal mode and seeing how much performance improves to pin down the problem add-ons.

Mozilla Firefox: Click the Firefox button, point to Help, and select Restart with Add-ons Disabled.

Google Chrome: To launch Chrome in Safe Mode, right-click the Chrome icon on your taskbar, right-click the Google Chrome option in the list, and select Properties. Add –no-extensions (beginning with two dashes) to the end of the Target box and click OK. Close all running Chrome instances — including the Chrome icon that may be running in your system tray – and then use the shortcut to relaunch Chrome. To disable safe mode, edit the shortcut again and restart Google Chrome.

Internet Explorer: On Windows 7, click the Start button and launch the All Programs -> Accessories -> System Tools -> Internet Explorer (No Add-ons) shortcut. On Windows 8, you’ll need to launch this program manually — press Windows Key + R to open the run dialog, type the following text into it, and press Enter:

iexplore.exe -extoff

Browser extensions can be useful. But, like any other software that remains running in your computer, you should try to only use browser extensions that you need.

The fewer browser extensions you have installed, the less bogged down your browser will be. Using a few lightweight extensions shouldn’t result in a noticeable difference on modern computers, but if you keep adding extension after extension, you’ll eventually see your browser slow down.