Mac Crawls When Photoshop Is Open? Here's What to Try First

Photoshop’s been around longer than most operating systems people use today. Its file format, its scratch disk system, its undo history — they were designed when 1GB of RAM was a lot and SSDs didn’t exist. Adobe has updated the engine many times, but the bones of how Photoshop allocates memory and writes to disk haven’t changed fundamentally.

That matters on a Mac because Photoshop will happily consume every byte of RAM you give it, then start writing gigabytes of scratch data to your SSD. On a 16GB Mac with a half-full 256GB drive, opening a few large PSDs can grind everything to a halt.

How Photoshop Uses Your Mac’s Memory

Photoshop manages its own memory allocator separate from macOS. By default, it claims 70% of your available RAM. On a 16GB Mac, that’s about 11GB reserved purely for Photoshop. The remaining 5GB has to feed macOS, your browser, your communication apps, and everything else.

Open Activity Monitor while Photoshop is running and you’ll see “Adobe Photoshop 2026” (or whatever year) with a memory footprint that grows as you work. Each PSD you open adds roughly:

• The image’s resolution × bit depth × channel count, in RAM
• Multiple history states (default 50, each a partial copy of layer data)
• Smart Object source data, sometimes duplicated
• Adjustment layer previews, brush previews, font caches

A 30MB PSD on disk can easily occupy 800MB in RAM once you’ve made a few dozen edits. Open four PSDs at once and you’re at 3-4GB just for content, on top of Photoshop’s base footprint.

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The Scratch Disk: Photoshop’s Hidden Weight

When Photoshop runs out of RAM, it writes the overflow to a “scratch disk” — a temporary file on your drive. Default location is your boot drive (the same SSD running macOS). On heavy edits, this scratch file can balloon to 30-50GB.

You can see it in real time. While Photoshop is running:

ls -lh /private/var/folders/*/T/Photoshop\ Temp*

Or, more practically, watch your disk free space drop while you work. That’s the scratch disk eating into it.

When your boot drive is the scratch disk and your boot drive is also where macOS swaps virtual memory, you have two systems competing for the same SSD. macOS slows down because its swap is contending with Photoshop’s writes. Photoshop slows down because macOS is swapping in the same area Photoshop wants to use.

The fix: give Photoshop a separate scratch disk. If you have:

• An external SSD with USB 3.2 or Thunderbolt — use it
• A second internal drive (rare on modern Macs, common on older ones) — use it
• Just the boot drive — make sure it’s at least 30% empty

To set it: Photoshop > Settings > Scratch Disks. Check additional drives if available.

Photoshop’s Settings That Actually Matter

Most Photoshop performance tweaks live in a single panel: Photoshop > Settings > Performance. The defaults are conservative.

1. Memory Usage — defaults to 70%. On a Mac with 16GB+, push to 80-85%. On 8GB, leave it at 70% or lower
2. History States — defaults to 50. Drop to 20 if you’re not heavy on undo. Each state is a partial layer copy
3. Cache Levels — defaults to 4. For high-res images (>50MP), bump to 6. For lots of small files, drop to 2
4. Cache Tile Size — 1024K is good for high-res photo work. 128K for detailed digital painting
5. Use Graphics Processor: ON — enables GPU-accelerated filters and transforms
6. Advanced Settings > Drawing Mode: Advanced unless you have visual glitches

Restart Photoshop after changing memory or cache settings. They don’t apply on the fly.

Why Photoshop Slows Other Apps Down

Photoshop’s resource use isn’t contained to its own window. Three things spill out:

1. Memory pressure — when Photoshop holds 11GB on a 16GB Mac, macOS aggressively compresses and swaps everything else. Your browser feels laggy. Slack feels delayed. The whole system gets slower
2. Disk I/O contention — heavy scratch disk writes saturate your SSD’s queue. Every other app waits longer for reads and writes
3. GPU contention — if Photoshop is using the GPU for a heavy filter, your video calls and animations stutter

The fix: when working on a large Photoshop file, close other heavy apps. Quit Chrome or Firefox. Quit Slack. Quit Spotify. Photoshop will use the freed resources and other apps won’t be fighting for them.

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Cleaning Photoshop’s Caches Outside the App

Beyond scratch disks, Photoshop accumulates cache and temp data in:

• ~/Library/Application Support/Adobe/Adobe Photoshop 2026/ — settings, brushes, presets
• ~/Library/Caches/com.adobe.Photoshop/ — image cache
• ~/Library/Preferences/Adobe Photoshop 2026 Settings/ — workspace and preferences
• /Users/Shared/Adobe/CameraRaw/ — Camera Raw cache, can hit 10GB+
• /private/var/folders/*/T/Photoshop Temp* — scratch files (cleaned on quit, sometimes orphaned)

Camera Raw cache is the surprise hit. Open Camera Raw > Preferences > Performance > Maximum size of cache — default is 5GB but it grows. Check the actual folder size; sometimes cleaning here recovers 10-20GB.

The orphaned scratch files are worse. If Photoshop crashes (it does), it leaves Photoshop Temp* files behind. Reboot doesn’t always clean them. Sweep’s smart scan finds these orphaned scratch files and shows their exact size before clearing.

Common Slowdown Scenarios and Fixes

Smart Objects multiply your memory cost. A Smart Object holding a 50MB raw file uses memory for both the source and the rendered preview. If you have ten Smart Objects in a single PSD, that’s 500MB minimum. Rasterize ones you don’t need to re-edit.

Adjustment layers are cheap, but blend modes aren’t. Multiply, Screen, and Overlay are fast. Color Dodge, Color Burn, and Hard Light require multiple per-pixel calculations and slow down on large images. Dissolve is the slowest blend mode you can pick.

Layer styles compound. Drop Shadow + Inner Glow + Stroke + Outer Glow on a single layer means four full-canvas effect renders every time the layer updates.

Camera Raw’s “Boundary Warp” and “Geometry” are CPU killers. They run on every preview update.

The Properties panel polls constantly. Switching layers updates it; on a complex doc, that’s a lot of work.

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A Diagnostic for When Photoshop Hangs

When Photoshop beach-balls and stays beach-balled:

1. Check Activity Monitor. Is Photoshop “Not Responding” or just busy? If just busy, wait — large filters can take a while
2. Check disk free space. Below 5% free on the boot drive, the scratch disk runs out and Photoshop hangs
3. Check memory pressure in Activity Monitor’s Memory tab. Red pressure means swap is thrashing
4. Check the document. A single 200MP image with 50 layers will tax even an M3 Max
5. Force quit if needed (Cmd+Option+Esc). Photoshop autosaves to recovery files at ~/Library/Application Support/Adobe/Adobe Photoshop 2026/AutoRecover/ — you usually won’t lose more than a minute of work
6. After force quit, manually clean orphaned Photoshop Temp files
7. Restart Photoshop and reopen the recovered file

What Older Tutorials Get Wrong

A few things you’ll see suggested that don’t help much in 2026:

• “Disable thumbnails” — modern Photoshop renders thumbnails efficiently, this barely moves the needle
• “Disable font preview” — only matters if you have thousands of fonts
• “Set GPU compatibility mode to Basic” — only useful if you’re seeing visual glitches
• “Increase cache levels to 8” — increases RAM use without speeding most workflows
• “Disable plugins” — disable third-party plugins, sure, but built-in plugins aren’t the problem

The biggest wins are still: more RAM, an external scratch disk, fewer simultaneously open documents, and aggressive history pruning.

When You Need More Hardware

Honest moment: if you’re regularly working on 100MP+ images with 30+ layers on an 8GB Mac, no amount of tweaking will make Photoshop fast. RAM is the bottleneck. The minimum reasonable setup for serious Photoshop work in 2026 is 16GB; the comfortable setup is 32GB; the “everything just works” setup is 64GB.

Until you can upgrade, the strategy is to keep Photoshop’s environment lean: clean scratch disk, ample free SSD space, no unnecessary apps competing for RAM, and Photoshop’s own settings tuned to your specific workflow.

Sweep keeps the macOS side of that equation in shape — caches cleared, large old files surfaced, login items pared down. Photoshop will still be heavy. It just won’t have to fight macOS for what it needs.