Chrome pioneered the model and every modern browser now uses it: each tab, each extension and several internal services run as separate operating system processes. If one crashes, it takes down a tab rather than the browser, and a compromised page cannot read another site's memory.
That isolation is worth having. It also means fixed overhead per process, repeated dozens of times, and a memory column that looks like an emergency.
Why the total is larger than the parts
Activity Monitor makes this worse by design. Processes share memory - the browser engine itself is loaded once and mapped into every tab process - but the tool attributes that shared memory to each process it appears in.
So twenty tabs each showing 200 MB does not mean four gigabytes. A large part of that is the same memory counted twenty times. The real figure is meaningfully lower, and there is no easy way to see it in the standard tools.
This is the single biggest reason people conclude their browser is out of control when it is behaving normally.
The two numbers that decide whether it matters
Memory used is the wrong question. The right ones are memory pressure and swap.
If pressure is green, the browser using eight gigabytes is not a problem, whatever the number looks like. macOS is comfortable, and reclaiming that memory would gain you nothing you could perceive.
If pressure is yellow or red and swap is growing through the day, that is real, and the browser is usually the largest contributor. We covered reading those two properly in how much RAM a Mac actually needs.
Normal versus leaking
The distinction that matters, and it is about shape rather than size.
Normal: memory rises as you open tabs and falls when you close them. Peak usage tracks what you are doing. After closing thirty tabs the figure drops substantially within a minute or two.
Leaking: memory rises through the day and does not fall when tabs close. A browser sitting at six gigabytes with four tabs open, having been at one gigabyte with the same four tabs this morning, is leaking - and the culprit is almost always a single page or extension rather than the browser.
The test is direct: quit the browser entirely and reopen it with the same tabs. If usage is dramatically lower, it was accumulation rather than requirement.
Finding the specific offender
Every major browser has its own task manager, and it is far more useful than Activity Monitor here because it names tabs and extensions rather than showing twenty identical helper processes.
- Chrome and Edge: Window menu → Task Manager.
- Firefox:
about:processes. - Safari: Develop menu → Web Process per tab, if the Develop menu is enabled.
Sort by memory and look at the top three. In practice you will find one of: a video call that has been open since a meeting ended, a document editor with a large file, a dashboard that polls continuously, or an extension.
Extensions deserve particular suspicion. They run on every page, they are frequently written casually, and a leaking extension shows up as steadily rising usage that no tab explains.
What actually reduces it
Close tabs, genuinely. Not minimise the window. A tab you have not looked at in three weeks is a bookmark you have not made.
Turn on tab discarding. Chrome's Memory Saver and Safari's equivalent unload inactive tabs and reload them when clicked. Costs a second on return and returns most of the memory.
Audit extensions. Disable them all, then re-enable the ones you notice missing. Most people are running several they installed once and never think about.
Restart the browser occasionally. Unfashionable advice and effective. A browser that has been running for two weeks has accumulated things that a fresh one has not.
Use separate profiles or windows for separate work. Mainly a discipline aid - it makes it obvious when a set of tabs is finished with.
Does switching browsers help?
Modestly, and less than the internet suggests.
Safari is generally the most memory-efficient on macOS, because it is tuned for the platform and integrates with the system's memory management more closely. The difference is real and it is a matter of tens of percent, not multiples.
Firefox and Chrome are broadly comparable. Any browser with forty tabs and eight extensions will use a lot of memory, because that is what you have asked it to hold.
The honest summary: switching browsers to save memory is treating a symptom. Forty open tabs is the input, and no browser makes that free.
When it is genuinely worth acting
Three signals, any one of which justifies the ten minutes:
- Memory pressure regularly yellow or red during ordinary work.
- Swap growing to several gigabytes through the day.
- Browser memory that does not fall when you close tabs.
Absent those, a large number in Activity Monitor is a browser doing what it was designed to do, and the correct response is to leave it alone.