I make a Mac memory tool, so questions about sudo purge land in my inbox fairly often. Usually from someone who ran it expecting a big result, got a small one, and wants to know why. The answer is honest and a little anticlimactic.
sudo purge is real, it's safe, and it's been part of macOS since Mavericks (10.9, 2013). It was originally intended for developers testing their apps: run purge, get a clean memory state, see how your app behaves when caches are cold. It was never designed as a user-facing speed-up tool. The memory cleaner industry adopted it and put it behind friendly buttons, which is where the confusion began.
What sudo purge actually does
When you run sudo purge in Terminal, you're telling the kernel to evict inactive memory pages from the cache. Specifically, it flushes two kinds of cached memory:
- File-backed pages: copies of files that are already on disk, cached in RAM for speed. If evicted, they can be reloaded from disk when needed.
- Anonymous pages: memory pages that were allocated by apps but are no longer actively in use, and that macOS has marked as "inactive" candidates.
The key word is "inactive". sudo purge only touches memory that macOS has already decided isn't doing anything urgent. It cannot touch memory that's actively in use by a running app. It won't fix a memory leak. It won't give back RAM an app is holding onto. It evicts the quiet stuff sitting in the waiting room.
After running purge, Activity Monitor will show more "free" (white) memory and less "cached" (yellow) memory. That's accurate. The question is whether that cached memory was costing you anything in the first place.
Why it worked better on Intel
The older guides recommending sudo purge were written for Intel Macs, often ones running spinning hard drives or the early Core 2 Duo and i5 generation. On those machines, the effect was noticeable: freeing 200-500 MB of RAM was common, and on a machine with only 4 GB total, that mattered.
Two factors made the Intel-era result larger:
Less aggressive automatic management. macOS's memory management has improved significantly across versions. Older versions of OS X were more conservative about releasing cached pages; cached data would linger longer than it needed to. There was more genuine stale memory for purge to find.
No unified memory architecture. Intel Macs separated CPU and GPU memory. The CPU RAM pool was smaller and more contested. Releasing even modest amounts had a visible effect. There was also less memory compression happening, which meant inactive pages occupied full physical space rather than being squashed down.
On a 2015 MacBook Pro with 8 GB RAM and an SSD, running sudo purge before a memory-intensive task made a measurable difference. That era is what gave the command its reputation.
The Apple Silicon reality
On M1, M2, M3, and M4 Macs, the situation is different in almost every relevant way.
macOS already releases memory aggressively. Apple Silicon runs a tighter memory management loop. The kernel is faster at identifying and evicting inactive pages before they pile up. By the time you type sudo purge, most of the easy wins have already been taken.
Unified memory changes the maths. Apple Silicon uses a single pool of high-bandwidth unified memory shared between the CPU, GPU, and Neural Engine. The architecture is designed to make every gigabyte count more. The OS is correspondingly more active about keeping that pool efficiently used.
Memory compression is aggressive. macOS compresses inactive memory pages in place rather than evicting them immediately. A page that would have been 4 KB is compressed to 1-2 KB and stays in RAM. This means your Mac can appear to have less "free" memory while actually handling more load than the numbers suggest. sudo purge sees less to evict because the system has already compressed it.
The result: on a modern Apple Silicon Mac, sudo purge typically reclaims 50-200 MB at best, and often far less. On a machine with 16 GB of unified memory, that's a rounding error.
What those "freed" numbers are really showing
Some memory cleaner apps display figures like "2.3 GB freed" after running their cleaning routine. Here's what that number usually represents:
They measure the change in a memory category (often "wired + active + inactive" compared to "free") before and after running their operation. If cached memory drops from 6 GB to 4 GB, they report "2 GB freed". But that cached memory was already the system's safety buffer. Evicting it doesn't mean you now have 2 GB more to use productively; it means the cache is cold and will refill as you keep working.
Within 10-15 minutes of normal use, the cache is back where it was. Nothing was saved. The number was real; the implication was misleading.
This doesn't make every memory cleaner app dishonest. But it's worth understanding what those figures represent before treating them as evidence of a problem solved. See the guide to memory pressure for a clearer picture of which numbers actually matter.
What works better on modern Macs
If your Mac feels sluggish and you're hoping sudo purge will fix it, the more likely causes are:
Apps holding memory after you've stopped using them. Many apps launch helper processes that continue running in the background, holding onto RAM, after the main app window is closed. These aren't caught by sudo purge because the memory is still "active" as far as the kernel is concerned. Quitting those processes properly makes a real difference.
Genuine memory pressure. If the Memory Pressure graph in Activity Monitor is consistently yellow or red, your Mac is under real load. sudo purge won't fix this. Closing applications, or buying more RAM if your Mac allows it, is the only real fix. See how to free up RAM on Mac for a practical walkthrough.
A process with a memory leak. If one app is consuming increasingly large amounts of RAM over time (common with browsers left open for days, or some Electron apps), purge will not help. The leaking app will simply grab more memory after purge runs. You need to identify and quit the leaking process.
For the orphaned-process problem specifically, a tool that identifies and pauses idle background processes does something sudo purge cannot: it targets active memory that's being held unnecessarily, not just inactive cache that macOS was about to reclaim anyway. That's the gap Shiny is designed to fill. See how to clear memory on Mac without restarting for a comparison of approaches.
And if you're evaluating memory cleaner apps more broadly, the honest case for and against Mac cleaners is worth reading first.
Should you bother running it?
Running sudo purge won't hurt anything. If you're curious, try it. Open Activity Monitor, note the memory numbers, run purge in Terminal, watch the numbers change. It's a useful demonstration of how macOS categorises memory.
But as a regular maintenance habit, or as a fix for a Mac that feels slow, it's not the right tool for 2026 Apple Silicon machines. The command is legitimate; the expectations around it haven't kept up with how much macOS has improved.
The original use case, flushing the cache before developer testing, is still valid. For everything else, the effect is too small to notice in practice.
For context from Apple's own documentation on how macOS handles memory pages, the deep-dive on macOS memory pressure by Jonathan Levin is the most thorough technical reference available outside of Apple's private documentation.