Mac Slow When the Photos Library Is Open? Try These Fixes

A small library of personal snapshots and Photos is fine. A library that’s accumulated 15 years of pictures, four iPhones’ worth of HEIC files, raw imports from a DSLR, screenshots, and short videos is a different story. Open Photos on a Mac with a large library and you’re asking the app to manage tens of thousands of items, run face recognition, scene classification, and Memories generation, all while sync may also be running to and from iCloud.

The result is one of the most consistently CPU-hungry apps in the macOS default suite. Most slowdowns trace back to one of a few specific operations.

What Photos Runs in the Background

Open Activity Monitor with Photos active and you’ll see:

• Photos — main app
• photoanalysisd — face, scene, and object analysis (the heavy one)
• photolibraryd — manages the library database
• mediaanalysisd — analyzes Live Photos and videos
• cloudphotosd — iCloud Photos sync
• AMPArtworkAgent (occasional) — generates thumbnails

photoanalysisd is the process that runs face recognition, scene classification, and other ML analysis on your photos. It’s deliberately low-priority — Apple wants it to use idle time, not block your work. But when it’s catching up on a backlog of 5,000 new photos, “low priority” still means significant resource use.

For a freshly imported library, photoanalysisd can run for hours or even days, intermittently spiking to 80%+ CPU.

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Photos Library Size: The Single Biggest Variable

Find your library at ~/Pictures/Photos Library.photoslibrary. Right-click > Get Info to see total size. For active families, libraries of 100-500GB are normal. For photographers, 1TB+.

Inside the library:

• originals/ — your actual files
• resources/ — caches, thumbnails, previews
• database/ — SQLite databases tracking everything
• caches/ — additional caches for various features

The database is the surprise hit. For a library with 100,000 items, the database can hit 2-3GB on its own. Every Photos query (search, smart album, switching to Memories) hits this database.

When the database is large, Photos can take 30-60 seconds to launch as it loads metadata.

Why Memories and People Burn CPU

Photos has several ML-driven features that run in the background:

1. People — face detection on every photo, then clustering similar faces
2. Memories — selects highlights and creates auto-generated montages
3. For You suggestions — featured photos, suggested edits
4. Search — object and scene recognition for natural language search
5. Live Text — text recognition in images
6. Visual Look Up — identifying landmarks, plants, animals

Each new photo triggers all of these. For an import of a few hundred photos, the analysis queue grows substantially. photoanalysisd works through the queue when the Mac is plugged in and idle.

If you actively use the Mac during this time, analysis takes longer. If you let the Mac sit plugged in overnight, analysis often catches up.

You can see analysis progress: open Photos, scroll to the very bottom of the sidebar (or the photo grid). At the very bottom, Photos sometimes shows messages like “Analyzing 1,234 items” or “X items remaining.”

iCloud Photos: The Multiplier

When iCloud Photos is enabled, Photos doesn’t just manage local files — it coordinates with Apple’s servers and other devices on your account. Every change has to:

1. Upload to iCloud
2. Notify other devices
3. Trigger analysis on those devices too
4. Potentially download missing originals if Optimize Mac Storage is on

For a Mac with iCloud Photos, you’re often seeing photoanalysisd processing photos that came in from iPhone, plus cloudphotosd uploading any new local additions, plus mediaanalysisd handling videos.

If you have multiple Macs on the same iCloud Photos account, all of them are doing analysis on the same photos — there’s no shared analysis state. This is wasteful but unavoidable.

Optimize Mac Storage: The Trade-Off

iCloud Photos > Optimize Mac Storage downloads only thumbnails locally; full originals stay in iCloud and download on demand.

Trade-offs:

• On: saves disk dramatically. A 500GB library might use 50GB locally
• Off: full originals always local. Faster to access, way more disk

The catch: when Optimize is on and you scroll through old photos, Photos has to download originals from iCloud. If you scroll fast through hundreds of old photos, you’re triggering hundreds of downloads. The Mac feels slow because it’s actively waiting on Apple’s servers.

For Macs with adequate space, “Download Originals” is a smoother experience. For Macs that are space-constrained, Optimize is essentially required.

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When Photos Won’t Stop Spinning

A common scenario: you imported a batch of photos a week ago, and Photos is still running photoanalysisd at high CPU. The cause is usually:

1. You don’t give the Mac idle time — analysis only runs when the Mac is unused
2. The Mac is on battery often — analysis pauses
3. A specific file is causing analysis to fail and retry — rare but possible
4. Library database is corrupt — analysis loops without making progress

To accelerate analysis:

1. Plug in the Mac
2. Leave it overnight, lid open, screen locked
3. Don’t quit Photos before bed
4. Check progress in the morning — if “Analyzing N items” message is gone, it’s done

If analysis seems stuck:

1. Quit Photos
2. Open Activity Monitor and force-quit photoanalysisd
3. macOS will relaunch it
4. Sometimes this is enough to unstick it

Library Repair: When Photos Misbehaves

If Photos is consistently slow, crashes on launch, or shows wrong content:

1. Quit Photos
2. Hold Cmd+Option while launching Photos
3. Click “Repair” in the dialog
4. Wait — repair can take hours on a large library

The repair walks the library database, fixes inconsistencies, and rebuilds caches. It’s invasive but resolves persistent corruption issues.

For deeper problems:

1. Quit Photos
2. Open the Photos Library package (right-click > Show Package Contents)
3. Move the database/ folder out
4. Launch Photos. It will rebuild from originals
5. This takes hours on a large library but produces a clean state

Don’t do this without a backup of the library first.

Settings Worth Changing

In Photos > Settings:

• iCloud > Sync this Mac: depends on your iCloud strategy
• iCloud > Optimize Mac Storage: ON if space-constrained
• General > Show Holiday Events: OFF if you don’t want auto-collections
• General > Show Memories: OFF if you don’t want them generated

You can disable People analysis entirely, but doing so means losing the People feature. Most users want People; they just don’t want it running at the wrong moment.

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Cleaning Up Photos-Related Data

Beyond the library itself, Photos generates caches and temp data:

• ~/Library/Caches/com.apple.Photos/ — cache
• ~/Library/Caches/com.apple.cloudphotosd/ — sync cache
• ~/Library/Containers/com.apple.Photos/ — sandboxed data

These are safe to clear. Photos rebuilds what’s needed.

The Photos Library itself contains its own internal caches that grow over time. If your library has gotten enormous, the “rebuild” approach above can recover space, but it’s heavy.

Sweep finds Photos-related caches as part of its smart scan, including caches that linger from older Photos versions or libraries you’ve since moved.

A Diagnostic for Photos Slowness

When your Mac slows whenever Photos is open:

1. Check Activity Monitor. Note photoanalysisd, photolibraryd, mediaanalysisd
2. Check Photos status — bottom of the sidebar shows analysis state
3. Check disk free space — Photos needs working room
4. Plug in the Mac if on battery
5. Pause iCloud Photos sync if uploads are competing
6. Let analysis finish overnight with the Mac plugged in
7. Quit Photos when not actively in use if analysis is dragging
8. Repair the library if corruption is suspected

Long-Term Habits

To keep Photos from being a recurring slowdown:

• Cull aggressively. You don’t need 30 nearly-identical shots
• Delete screenshots regularly. They accumulate without you noticing
• Move very old photos to a separate library if you want to free analysis time
• Don’t import RAW from a camera into Photos if you have a real catalog tool
• Run Photos overnight occasionally to let analysis catch up

Photos is a great app for organizing personal photography, but it scales poorly past about 100,000 items. For larger libraries or specialty workflows, dedicated catalog tools (Lightroom, Mylio, Capture One) are faster and lighter — though they don’t have iCloud Photos integration.

For most Mac users, the answer is to keep Photos lean (cull regularly, manage library size), let analysis run when you’re not using the Mac, and occasionally rebuild caches when things get sluggish. Sweep handles the macOS side — the surrounding caches and language files that compound when Photos is also working hard. Together they keep Photos from being the daily drag it can become on a long-running Mac.