macOS Sequoia Running Slow? Here's What to Try

The first three weeks after upgrading to Sequoia are statistically the slowest your Mac will feel. macOS rebuilds Spotlight indexes, Photos analyzes faces, and (on supported Macs) Apple Intelligence downloads model files and indexes Mail and Notes. If you upgraded yesterday and your Mac feels rough, the answer is “wait three days, plug in overnight.”

If you upgraded three months ago and it still feels rough, that’s a different conversation. Here’s the diagnosis-first version.

Diagnose before you fix

Don’t start randomly clearing caches. Start with Activity Monitor. Apple menu → Activity Monitor (or Spotlight it). Watch the CPU tab for one full minute, sorted by % CPU.

Three patterns you’ll typically see:

1. One process dominating CPU — name it, search the name, address that specifically. Below.
2. Several processes evenly busy, total still high — likely an indexing or sync task; let it finish.
3. Nothing busy, but the Mac feels slow — disk space, memory pressure, or a system extension. Different fixes.

Identifying which case you’re in saves hours of guessing.

Pattern 1: One process is hogging CPU

Common Sequoia culprits and what they mean:

• mediaanalysisd — Photos analyzing faces, scenes, and objects. Will finish on its own. Plug in, leave overnight.
• bird — iCloud Drive sync. Pause it (System Settings → iCloud) if you’re trying to do other things.
• cloudd — same family as bird, broader iCloud sync.
• WindowServer — too many displays, or transparency. Reduce transparency in Accessibility, restart.
• mds_stores — Spotlight reindex. If it’s been hours, force a clean rebuild (below).
• AppleIntelligenceModelD or similar — Apple Intelligence indexing. Will finish in 24–72 hours after first enabling.
• VTDecoderXPCService — video decoder. A web video stream stuck open in a hidden tab. Quit your browser to confirm.
• safari-wasm — a single Safari tab using WebAssembly heavily. Find the tab.

Most of these are temporary. The exception is WindowServer, which usually means a settings change is needed, and any third-party process — quit it, disable it, decide whether you actually need it.

Pattern 2: Indexing or sync in progress

If you upgraded recently or migrated from another Mac, the first 1–3 days will show high background activity. This is normal and you should let it finish.

What’s running:

• Spotlight index of your entire user folder
• Photos analysis of faces, scenes, and (on supported Macs) Visual Look Up
• iCloud Drive download of files marked “Download Now”
• Apple Intelligence model downloads (M1+ Macs, English locale)
• Mail rebuild of search index

If you can plug the Mac in and walk away for the night, do that. Most of this finishes in one undisturbed sleep cycle. Trying to use a Mac that’s mid-index is like trying to type on a Mac while it’s installing a major OS update — the underlying work has to finish.

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Pattern 3: Nothing busy but the Mac feels slow

This is the hardest case and usually maps to one of three things:

Disk space below 15% free

System Settings → General → Storage. If the bar shows under 15% free, that’s your problem. macOS uses free space for memory paging and APFS metadata. Below that threshold, every operation gets slower.

Quick wins: empty Downloads, empty Trash, delete old iOS backups (~/Library/Application Support/MobileSync/Backup/), trim Time Machine local snapshots.

Memory pressure constantly yellow or red

Activity Monitor → Memory tab → look at the pressure indicator at the bottom. If yellow or red is normal for you, you’ve outrun your RAM. The fix is fewer concurrent apps and tabs — not more software tweaks.

If you’re on 8GB and you feel like you should have more headroom: switch your daily browser to Safari (uses substantially less RAM than Chrome), close Slack when you’re not actively chatting, quit Spotify when you’re not listening.

A misbehaving system extension

System Settings → General → Login Items & Extensions → scroll down to Network Extensions, Driver Extensions, System Extensions.

Anything you don’t recognize, especially if it’s from a vendor you no longer use (old VPN, old antivirus, old screen recorder), disable it. These run with elevated privileges and can quietly cause problems years after you stopped using the app.

The Sequoia-specific things to check

A few items are unique to Sequoia and worth a separate pass:

iPhone Mirroring cache

If you’ve ever opened iPhone Mirroring, there’s a cache that grows but never shrinks.

1. Quit iPhone Mirroring.app entirely.
2. Finder → Cmd+Shift+G.
3. Paste: ~/Library/Group Containers/group.com.apple.iphonemirroring/
4. Move the Caches folder to Trash.

Recovers 5–8GB on heavy users.

Apple Intelligence — turn off if you don’t use it

System Settings → Apple Intelligence & Siri. If you don’t use Writing Tools, Image Playground, Genmoji, or Siri summaries, turn the whole feature off. The model files stay cached but the daemons stop running.

Window tiling

If dragging windows feels janky, the new tiling preview is the cause. System Settings → Desktop & Dock → Windows. Turn off “Drag windows to screen edges to tile” if it bothers you. Animation cost drops.

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The general checklist (post-upgrade hygiene)

After identifying the pattern, run through this list:

1. Restart, then check Activity Monitor again. Restart alone fixes about a third of post-upgrade issues.
2. Update to the latest 15.x point release. Apple has fixed several Sequoia performance bugs in 15.1, 15.2, and 15.3.
3. Audit login items. System Settings → General → Login Items & Extensions. Turn off background helpers you don’t need.
4. Clear the big caches — iPhone Mirroring, Slack, Chrome, Xcode DerivedData.
5. Reduce visual effects. Accessibility → Display → Reduce motion + Reduce transparency.
6. Check Spotlight. If mds_stores is busy for hours, force rebuild: sudo mdutil -E /
7. Free disk space if you’re under 20% free.
8. Check memory pressure. If yellow or red, close apps and tabs.

Roughly 80% of Sequoia slowdowns are resolved by some combination of those eight steps.

When it’s actually a hardware issue

A few signs that point to hardware, not software:

• Fans constantly at full speed even on the desktop — thermal management problem. Older Macs need fan/vent cleaning or thermal paste replacement.
• kernel_task at 200%+ on Intel Macs — same. The kernel is throttling because the Mac is too hot.
• Random freezes that require force-restart — could be RAM (rare on Apple Silicon, more likely on Intel) or a failing SSD.
• Slowdowns that align with battery draining — battery-related throttling. Genuine on aging laptop batteries.

For Intel Macs especially, if the Mac is more than 4 years old and you’ve never opened it up, dust in the fans is a real factor.

When to reinstall

If you’ve worked the list and Sequoia is still rough:

1. Safe Mode boot test. Apple Silicon: hold power, choose drive while holding Shift. If Safe Mode is fast and normal mode is slow, the culprit is something you’ve installed.
2. New user account. Create a fresh user, log in, use it for an hour. If it’s fast, your main user’s preferences or login items are the issue.
3. Reinstall macOS in place. System Settings → General → Transfer or Reset → Reinstall macOS. Doesn’t touch data; rewrites OS files. About 30 minutes. Fixes a surprising amount.

A reinstall is the closest you can get to a fresh Sequoia without losing your files. It’s worth trying before any more drastic step.

What not to bother with

• Disabling Spotlight entirely — you’ll miss it. Exclude specific folders if needed.
• Reset PRAM on Apple Silicon — there’s no PRAM. The combination doesn’t do anything.
• “Repair Permissions” — modern macOS doesn’t expose this for a reason; SIP handles it automatically.
• Periodic maintenance scripts via Terminal — macOS runs these automatically when idle. You don’t need to manually invoke them.

Sequoia rewards a methodical pass over a panicked one. Identify the pattern, fix the specific cause, then run through hygiene. Skipping the diagnosis step and going straight to “clear all the caches” usually recovers some space but doesn’t fix the speed problem.