Why Macs Get Slower Over Time (and How to Reverse It)

The story most people tell themselves is that Macs slow down with age. The hardware, they assume, just doesn’t keep up with newer software. There’s some truth to this — a 2014 MacBook Air really can’t run Sequoia 15 well, no matter what you do.

But the more interesting story is that most “my Mac got slower” cases aren’t about hardware aging. They’re about software state accumulating. The same chip that ran fast on day one is still capable of running fast on day 1,000. What changed is everything around the chip.

Here’s what actually happens between “fast new Mac” and “slow old Mac” — and how to undo it.

The accumulation, ranked

After 18 months of normal use, a typical Mac has gathered:

1. 40-80 launch agents — many from apps you’ve uninstalled
2. 15-30GB of cache files across browsers, apps, and the system
3. 5-15GB of log files that nobody reads
4. 2-8GB of language files for languages you don’t use
5. Hundreds of MB of preferences files, some corrupted
6. Many GB of leftover application support data from removed apps
7. A Spotlight index that’s grown beyond optimal
8. A Photos library doing background analysis on every imported batch
9. Login items you’ve forgotten about, each adding seconds to boot
10. Browser extensions you stopped using two years ago

None of these individually breaks anything. Together, they’re the difference between “fast” and “slow.”

Why it sneaks up on you

The slowdown is gradual. Day-over-day, you don’t notice. Six months later, you also don’t really notice — your sense of how fast the Mac “should” be has updated as the Mac has slowed. By the time you actively notice slowness, the accumulation is significant and the regression is dramatic if you compare to a fresh install.

This is why “set up a new Mac” feels so satisfying. The new Mac isn’t really faster — your previous Mac probably had the same speed potential. The new Mac just hasn’t accumulated state yet.

Doing a periodic deep clean produces the same effect on your existing Mac.

How to reverse it: the foundational cleanup

Block out an afternoon. Work through these in order.

Phase 1: Storage cleanup

System Settings → General → Storage. Click each category. Be ruthless about what you don’t need:

• Downloads — sort by size, archive what’s important, delete the rest
• iOS Files — old iPhone backups in ~/Library/Application Support/MobileSync/Backup/
• Trash — including in Mail and Photos
• Apps you don’t use anymore

Aim for 25-30% free.

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Phase 2: App cleanup

For each app in your Applications folder, ask: when did I last use this?

If it’s been months and won’t likely be used, uninstall properly. The right way is to remove not just the app but its support files. For each app being removed:

• The .app in Applications/
• Anything in ~/Library/Application Support/[app name]
• The preference plist in ~/Library/Preferences/
• The cache in ~/Library/Caches/[bundle id]
• The container in ~/Library/Containers/[bundle id] (for sandboxed apps)
• Any helpers in ~/Library/LaunchAgents/
• Any system-level helpers in /Library/LaunchAgents/ and /Library/LaunchDaemons/

This is honestly tedious. Tools like Sweep’s app uninstaller find every leftover file across these locations and let you approve removal in one pass.

Phase 3: Login items audit

System Settings → General → Login Items & Extensions. Disable anything you don’t actively need at login.

Then check launch agent folders for orphans (launch agents whose owning app is no longer installed):

• ~/Library/LaunchAgents/
• /Library/LaunchAgents/
• /Library/LaunchDaemons/

Drag suspect items to your Desktop, restart, test for a day, then trash if everything still works.

Phase 4: Cache and log cleanup

The big folders worth clearing:

• ~/Library/Caches/ — per-user caches (browsers, apps, system)
• ~/Library/Logs/ — log files
• /Library/Logs/ — system logs
• ~/Library/Containers/[app]/Data/Library/Caches/ — sandboxed app caches

For caches, almost everything is safe to delete — apps regenerate what they need. The risk is closing an app abruptly while it’s writing cached data.

For logs, mostly safe to delete. Some apps keep crash logs that might be useful for support; if you’ve never had to provide a crash log, you don’t need them.

Phase 5: Reset Spotlight

A long-running Spotlight index gets bigger and slower. A clean reindex usually improves search performance noticeably.

1. System Settings → Siri & Spotlight → Spotlight Privacy
2. Add startup disk
3. Wait 30 seconds
4. Remove startup disk

Reindexing takes hours — leave the Mac on overnight.

While you’re there, exclude folders that don’t need to be searchable. Big media folders, downloaded archives, VM disks, Docker volumes — all candidates for permanent exclusion to keep the index lean.

Phase 6: Disk First Aid

Applications → Utilities → Disk Utility → select startup disk → First Aid. Non-destructive. Catches filesystem issues that build up over time.

Phase 7: Browser cleanup

Open each browser you use:

• Clear browsing data (history, cookies, cache) — last 4 weeks at minimum
• Audit extensions — disable or remove ones you don’t use
• Check homepage and start page settings — sometimes hijacked by old extensions
• Reset to defaults if the browser feels bloated

For Chrome specifically, chrome://settings/reset will reset all settings to defaults without affecting bookmarks or saved passwords. Often surprisingly effective.

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How often to do this

A full deep clean every 6-12 months is plenty. Between deep cleans, do a light touch monthly:

• Empty Downloads folder of stuff you’ve moved or don’t need
• Empty Trash
• Restart the Mac if uptime is over 14 days
• Quick check of Activity Monitor for anything weird

That’s a 10-minute routine that prevents the gradual accumulation from becoming dramatic.

What you’ll notice afterwards

After a deep clean, expect:

• Boot time roughly cut in half (depending on how bad it was)
• Apps launch faster, especially second-time launches
• Less beachballing
• Better battery life on laptops (less background work)
• Free disk space — typically 20-50GB recovered
• Spotlight search actually finds things again
• General sense of responsiveness back to “normal”

The gain is most dramatic on Macs that have been in service 3+ years without periodic cleanup. The first deep clean on a 5-year-old Mac can feel like a hardware upgrade.

Why most people don’t do this

Honestly, it’s tedious. The steps above take 2-4 hours done by hand, and the dopamine reward of “deleted some cache files” is low. Most people give up halfway, do the easy parts, and end up with marginal improvement.

That’s the reason cleanup tools exist — they automate the boring parts so the cleanup actually gets done. Sweep specifically targets the categories above (caches, logs, language files, app leftovers, login items, large forgotten files) and does the scan in seconds. You see what it found, you approve what to remove, and you’re done in a few minutes instead of hours.

When this isn’t enough

Sometimes accumulated cleanup doesn’t fix things. Cases where the issue is genuinely hardware:

• SSD nearing end of life — typically 5-10 years on Apple Macs
• Battery degraded enough to throttle — under 80% capacity
• RAM that’s just genuinely too small for current workloads
• Chip too old for current macOS

But before assuming any of these, do the cleanup. Most “old, slow Mac” cases are software, not hardware. The hardware on your Mac is probably fine. The state surrounding it is the problem.

A Mac doesn’t have to get slower over time. It just typically does because nobody cleans it. Clean it, and the speed comes back.