How much memory do Chrome extensions actually use?

Extensions have a reputation for eating memory, and the advice that follows is usually “remove some.” That is not wrong, but it skips the part that would let you choose which. Extensions cost memory in two distinct places, and the place people check is the smaller of the two.

Cost one: the extension's own process

Every extension can run background code. Under Manifest V3 — mandatory for everything in the Chrome Web Store today — that code lives in a service worker, which Chrome starts when there is something to do and shuts down after roughly thirty seconds of idleness.

This matters more than it sounds. Under the old Manifest V2, a background page stayed resident for as long as the browser ran, holding its memory whether or not you used the extension that day. A well-built V3 extension holds nothing at all most of the time.

This is the cost you can see: press Shift + Esc with Chrome focused, and Chrome's task manager lists every extension by name with its memory footprint.

Cost two: content scripts, in every tab

The larger cost does not appear under the extension's name at all. Most extensions do their real work by injecting a content script into the pages you visit — that is how a password manager finds the login form, how a content blocker hides an advert, how a grammar checker reads a text box.

That script runs inside the page's process, and its memory is counted as part of the tab. So an extension adding 8 MB per page costs you 8 MB with one tab open and 240 MB with thirty. It never shows up as a large number next to the extension's name, because the cost is spread across every tab you have.

This is the mechanism behind the common experience of an extension seeming harmless in isolation and the browser being enormous anyway.

What is actually normal

• 10–60 MB for the extension process is typical and not worth worrying about.
• 100 MB+ is normal for a content blocker. Filter lists have hundreds of thousands of rules and they have to be in memory to be fast. You are getting real value for it.
• Hundreds of megabytes with no obvious reason deserves a look. So does an extension whose memory climbs steadily the longer the browser runs — that is a leak.

How to audit yours in five minutes

1. Open Shift + Esc and sort by Memory. Note anything surprising.
2. Open chrome://extensions and turn off — do not remove — the two or three largest, plus anything you do not recognise.
3. Use the browser normally for a day. If nothing broke and nothing was missed, remove them properly.
4. For the ones you keep, check whether they need access to every site. Many work fine set to “on click”, which stops the content script loading in every tab and eliminates the multiplied cost entirely.

That fourth step is the one people skip, and it is usually the largest saving available.

Our own footprint, since it would be strange not to say

MemoryStats is a Manifest V3 extension. Its service worker is asleep unless you have opened the panel or a scheduled cleanup is running, and it does not inject a persistent content script into your pages — it reads each tab's memory on demand rather than sitting inside every page waiting. Cleaning up other software's memory while quietly holding a few hundred megabytes of your own would rather defeat the point.

If you want to see where the rest of your memory is going, tabs are usually the bigger story — here is how to free up what they are holding, without closing anything.