Why Is My Brand New Mac So Slow: What Came Over From the Old One

A new Mac that is slower than the machine it replaced is a specific kind of frustrating, because every explanation that works for an ageing computer is unavailable. Nothing is worn out, the storage is nearly empty, and the benchmark numbers for the chip are public and good. Something else is going on, and it is almost always one of three things: work that only happens once and has not finished, software that came across from the old Mac and does not belong on this one, or an arrangement that was already too heavy and is now running on a machine that hides it less well than expected.

Telling those apart is worth doing before returning the Mac or opening a support case. Two of the three end on their own within days. The third never does, and no amount of waiting will fix it.

The machine is new, the workload is not

The setup process offers to bring everything over, and most people accept, because the alternative is a week of reinstalling. Apple is explicit about what that transfer includes.

Migration Assistant transfers documents, apps, user accounts, and settings from one Mac to another. It doesn't delete information from your old Mac or replace the operating system (macOS) on your new Mac. Source: support.apple.com

Read that list again with the word settings in mind. Settings include the list of things that open automatically at login, and the permissions granted to background helpers over the whole life of the old Mac. Every updater, sync agent, menu bar utility and cloud client that had accumulated across four or five years arrives intact and starts itself on the first boot. A machine set up from scratch runs a handful of background processes on day one. A migrated machine runs whatever the previous one ran, and the previous one was slow partly because of them.

The list is in one place. Choose Apple menu, then System Settings, then General in the sidebar, then Login Items and Extensions. The upper list holds items that open at login. The lower group controls which apps are allowed to run in the background, which Apple describes as performing tasks when the app is not open, such as checking for software updates or syncing data. Going through both lists on a new Mac is the single highest-value hour available, because the decisions are being made while it is still obvious which of these tools are actually in use.

Some of the first week is work that only happens once

A new Mac spends its first days doing things it will never do again, and all of it is invisible except as heat, fan noise and lag.

Files stored in iCloud are downloaded on demand, so the first time each folder is opened, the contents come over the network rather than off the disk. Photo libraries are re-analysed locally so that searching by face and object works. Mail re-downloads the messages it is configured to keep. Spotlight builds its index of everything that just arrived, and until that index is complete, searches are slower and less complete than they will be later. Any apps installed from the App Store check for updates and replace themselves.

None of this is a fault, and none of it can be usefully accelerated. What it means practically is that a judgement made on the first evening is not a judgement about the Mac. The useful test is to leave the machine awake, plugged in and connected for a few hours without using it, ideally overnight, and then form an opinion. If the Mac is normal after that and was sluggish before it, the answer was patience and nothing needed fixing.

The way to confirm it rather than guess is Activity Monitor, in the Utilities folder inside Applications. Sort by CPU and look at the names at the top during a slow period. Setup work shows up as system processes with recognisable jobs. A permanent problem shows up as an application.

Translated apps carry a cost, and that cost has a deadline

Apps that came over from an Intel Mac may not be built for Apple Silicon, in which case they run through translation rather than natively. Apple's own guidance is to stop relying on that.

For optimal performance and future compatibility, update your Intel-based apps by replacing them with a "Universal" or "Apple silicon" version of the app, instead of relying on Rosetta to translate the app for use with Apple silicon. Source: support.apple.com

The same page states the timeline plainly: Rosetta is available for any Mac with Apple Silicon using macOS 27 or earlier, and starting with macOS 28 its functionality will be available only for certain older, unmaintained games that rely on Intel-based frameworks. That turns a performance question into a planning question. An application that only exists as an Intel build is not just slower today, it has a limited number of macOS releases left.

Finding them takes a minute. Open the Apple menu, choose About This Mac, then System Report, then Applications, and look at the Kind column. Entries listed as Intel are the candidates. Most will have a Universal version available from the developer, and replacing those is worth doing during the first week while nothing depends on the current installation yet.

The browser did not arrive empty either

Signing into a browser on a new Mac restores the extensions, the pinned tabs and often the open session from the old one, which means the heaviest single application on the machine is reproduced exactly. That is convenient and it is also the fastest way to import the previous Mac's slowness into a new one without noticing.

Extensions deserve the most attention, because they run on every page and their cost is paid continuously rather than once. A new Mac is the only moment when the list is short enough to review honestly, so going through it and removing anything that has not been used in the last month is worth the ten minutes. The ones that inject content into every page, such as older ad blockers, page translators and grammar tools, are the ones to look at first.

Tabs are the other half. Chrome ships a setting built for this in its Performance section. Memory Saver deactivates tabs that are not in use and reloads them automatically on return, with three levels available: Moderate, which lets tabs go idle after a longer period, Balanced, which Google marks as recommended, and Maximum, which deactivates them sooner. The same screen holds a list of sites that are always active, for pages that must never reload.

There is a limit to how much that setting can help, and Google documents it. Tabs are not deactivated while audio or video is playing, during a call or screen share, with page notifications active, while a download is running, when a form is partly filled in, when the tab is pinned, or when a USB or Bluetooth device is connected. A chat application kept as a pinned tab matches several of those conditions at once, which is why the tabs that cost the most are the ones the setting is designed to leave alone. On a machine whose working day is built out of exactly those applications, the answer is not a browser setting but a different arrangement.

What the Memory tab says about a brand new Mac

Base configurations have the memory they have, and the number is often the same as, or smaller than, the machine being replaced. A new Mac with less installed memory than the old one can lose on this one axis while winning on every other.

Open Activity Monitor and click Memory. Memory Used sitting close to the installed total is normal on every Mac, because macOS fills otherwise idle memory with cached files. The figures that carry information are Memory Pressure, which Apple defines as a graphical representation of how efficiently memory is serving processing needs, determined by free memory, swap rate, wired memory and file cached memory, and Swap Used, which is space on the startup disk being used to move unused files in and out of RAM. Pressure spiking with gigabytes of persistent swap during ordinary work means the workload is above what this configuration holds, and on Apple Silicon that cannot be changed after purchase, because the memory is part of the chip package.

That measurement is worth taking within the return window rather than after it.

Which problems end by themselves

What is happening	Where to look	Does it end on its own
Fans and lag for the first day or two	Activity Monitor, system processes at the top	Yes, once indexing and downloads finish
Slow for ten minutes after every login	Login Items and Extensions	No, until the list is pruned
One app is slow, others are fine	System Report, Applications, Kind column	No, needs a Universal build
Everything lags with several web apps open	Memory tab: Swap Used and pressure	No, this is a configuration limit
Nothing measurable, work still feels heavy	How windows and accounts are arranged	No, this is not a hardware problem

The bottom row is the one that survives every clean install, and it is the one most often mistaken for a hardware fault.

When the Mac is fine and the arrangement is not

There is a version of this complaint where every measurement comes back clean. Memory Pressure is flat, no process is above a few percent, the fans are quiet, and the working day still feels slow. What is slow in that case is not the computer, it is the act of finding things in it.

A working day spent in web applications, where a mail client, two chat workspaces, a project board and a documents app are all open as tabs, spends a surprising amount of time on retrieval. Locating the right tab takes a second or two, and it happens dozens of times an hour. Signing out of one account to reach another on the same service takes longer. None of this registers as load, so it survives the new Mac completely intact, which is exactly why the upgrade disappointed.

The alternative is an arrangement where each web application holds its own window and its own session rather than competing for space in a tab strip, so accounts stay signed in side by side and every tool is where it was left. That is the idea described on the Workspaces page, and the difference from tab grouping is the point of it. Whether the specific set of tools a day is built on can work that way is answerable in advance from the Supported apps list.

What to change first

Give the Mac one full night awake and connected before judging it, then go through Login Items and Extensions line by line, since that list arrived from a machine that had years to fill it. If the day still feels slow once both are done and Activity Monitor shows nothing loaded, the thing to change is the arrangement rather than the hardware, which is what SpaceDeck is built for.