Quick Folder Preview · Troubleshooting

Quick Look Not Working on Mac? Here's Every Fix That Actually Works

Blank previews, a frozen spinning wheel, or Space just selecting the file instead of opening it. Nine fixes, in the order actually worth trying them, including a macOS 26 Tahoe bug most guides never mention.

By Ram Velmurugan · Founder & Lead Developer, 1dot.ai

Verified against macOS 26 Tahoe·Updated August 2026·9 min read

Quick answer: Most Quick Look failures come down to one of three things: a stuck quicklookd process, a corrupted preview cache, or, new-ish and rarely mentioned, Full Keyboard Access silently swapping what the space bar does. Relaunching Finder and running qlmanage -r cache in Terminal clears up most cases in under a minute. If pressing Space just draws a blue selection box around the file instead of previewing it, that's a different bug entirely: turn off Full Keyboard Access under System Settings > Accessibility > Keyboard instead.

Editorial note: 1dot.ai is building Quick Folder Preview, a folder-first preview app for Mac mentioned briefly near the end of this guide. It is not available to download yet, only a waitlist, and it plays no role in the fixes below. Every command, setting location, and bug report referenced here was checked live in August 2026 against Apple's own documentation and user reports; sources are listed near the bottom.

Why Quick Look Breaks in the First Place

Quick Look isn't one thing, it's a small pipeline: you press Space, Finder asks a background process called quicklookd to generate a preview, that process hands the file to whichever plugin knows how to render its format, and the result gets cached so the next preview is instant. Any link in that chain can break on its own, which is why "Quick Look isn't working" can mean several genuinely different problems depending on exactly what you're seeing.

That's the reason a single blanket fix like "just restart your Mac" only works some of the time. The rest of this guide is organized by what you're actually seeing, from the fastest, most common fixes to the rarer ones, plus a Full Keyboard Access bug on macOS 26 Tahoe that produces a symptom, a blue selection box where a preview should be, easy to mistake for Quick Look being broken when it isn't.

Table of Contents

A 15-Second Check First
The Fixes, in Order
Symptom → Cause → Fix
Where Quick Folder Preview Fits In
Sources & Further Reading
FAQ

A 15-Second Check First

Before touching Terminal or System Settings, rule out the obvious: click directly on a single file so it's actually selected (a multi-file selection or an empty area won't trigger Quick Look at all), then press Space once. If you're on a laptop with an external keyboard attached, make sure you're pressing the space bar on the keyboard macOS is actually listening to. It sounds trivial, but it's the fastest way to skip straight past a real fix you don't actually need.

One thing to notice

If Space does something, just not a preview, specifically if it draws a blue outline around the file instead, skip ahead to the Full Keyboard Access fix below. That symptom has a specific cause and none of the cache or process fixes above it will touch it.

The Fixes, in Order

Relaunch Finder

This is the fastest thing to try and it solves more Quick Look problems than any other single step, because Finder and Quick Look share process state, and a stuck Finder process is the most common reason Quick Look stops responding entirely.

Option-Control-click (or right-click while holding Option) the Finder icon in the Dock and choose Relaunch. If Finder is completely unresponsive, use the Apple menu > Force Quit, select Finder, and it restarts itself automatically since it's always running.

Fixes: nothing previews, Quick Look freezes

Clear the Quick Look Cache

Every preview Quick Look generates gets cached so it doesn't have to redraw it from scratch each time. If one entry in that cache gets corrupted, usually after a crash or a forced shutdown, you get a blank or gray box for that file, or sometimes for every file of a particular type.

Open Terminal (Spotlight search for it, or find it in Applications > Utilities) and run:

qlmanage -r cache

That clears the thumbnail cache without touching your actual files. Give it a few seconds, then try Quick Look again.

Fixes: blank or gray previews, one file type broken

Turn Off Full Keyboard Access (the Blue-Box Bug)

This is the fix most Quick Look troubleshooting guides skip entirely, and it's the one to try first if pressing Space draws a blue selection outline around the file instead of opening a preview. It isn't a broken Quick Look install. It's Full Keyboard Access reassigning what the space bar does system-wide.

Multiple Mac users reported this exact symptom on macOS 26 Tahoe on Apple's own community forums in late 2025, and it isn't new: the same Full Keyboard Access conflict has resurfaced on and off since Monterey. Once Full Keyboard Access is on, macOS sometimes treats Space as "activate the focused control" instead of passing it through to Quick Look, and the effect shows up outside Finder too, including as unexpected spacebar behavior in some other apps.

Open System Settings > Accessibility > Keyboard and turn Full Keyboard Access off. The fix is instant, no restart needed, and Space goes back to triggering a normal Quick Look preview the moment you toggle it.

Fixes: space bar selects instead of previewing

Fully Reset the Quick Look Server

If clearing the cache alone doesn't help, or Quick Look shows "Preview Not Available" for files that should work fine, quicklookd itself, the background process that actually generates previews, may need a full restart along with a rebuild of its plugin list.

qlmanage -r

Note there's no `cache` argument this time. This resets the server process and forces it to re-scan every installed Quick Look preview plugin, which is a heavier fix than clearing the cache and covers more ground.

Fixes: every file shows "Preview Not Available"

Force Quit the Quick Look Processes Directly

If a specific preview window is frozen or Quick Look hangs on one file rather than failing outright, open Activity Monitor (Spotlight search, or Applications > Utilities) and search "quicklook". You'll typically see QuickLookUIService, the process that renders the actual preview window, and com.apple.quicklook.ThumbnailsAgent, which generates Finder thumbnails.

Select the stuck process and click the X (Force Quit) in the toolbar. macOS relaunches these processes automatically the instant you trigger another preview, so there's no downside to force-quitting them.

Fixes: Quick Look hangs, spinning wheel, one preview stuck open

Force iCloud Files to Finish Downloading

If "Optimize Mac Storage" is turned on for iCloud Drive, macOS quietly offloads files you haven't opened in a while and leaves a placeholder in their place. Finder still shows the file's name and icon, so it looks present, but Quick Look can only preview what's physically on your disk.

Look for a small cloud-with-down-arrow badge on the file's icon; that's the tell. Click the file once to trigger the download, wait for the badge to disappear, then try Quick Look again. If this happens constantly and it's disruptive, you can turn Optimize Mac Storage off entirely under System Settings > [your name] > iCloud > iCloud Drive, at the cost of using more local disk space.

Fixes: cloud files show "Preview Not Available"

Find and Disable a Broken Quick Look Extension

A third-party Quick Look extension, the kind that adds preview support for code files, Markdown, or a specific document format, can conflict with the system or simply stop working after a macOS update. This is also where the old-style legacy plugins some users still have installed cause problems: Apple dropped support for the older .qlgenerator plugin format starting with macOS 15 Sequoia, and that break carries through macOS 26 Tahoe with nothing reversed.

Open System Settings > General > Login Items & Extensions, scroll to the Quick Look section, and disable extensions one at a time, testing after each, to isolate which one is causing trouble. If you're running one of the free community Quick Look plugins distributed through Homebrew, it's also worth checking whether it's still actively maintained; a growing number were flagged in 2026 for failing Apple's notarization requirements.

Fixes: Quick Look crashes Finder, or only certain file types fail

Boot Into Safe Mode to Confirm a Third-Party Conflict

Safe Mode starts macOS with only Apple's own software running, no third-party extensions, login items, or fonts. If Quick Look works normally in Safe Mode, something you've installed is the real cause, not macOS itself, and you can narrow it down by re-enabling apps and extensions in batches.

On Apple Silicon Macs, shut down completely, then press and hold the power button until "Loading startup options" appears, choose your startup disk, and hold Shift while clicking Continue in Safe Mode. On Intel Macs, restart and hold Shift immediately after the startup chime.

Fixes: confirms the cause when nothing else has worked

Update macOS, Then Reinstall as a Last Resort

If every fix above has been tried and Quick Look still fails consistently, check System Settings > General > Software Update for a pending macOS update first; Apple has patched specific Quick Look regressions in point releases before without a formal changelog entry.

Reinstalling macOS through Recovery Mode (hold Command-R on Intel, or the power button on Apple Silicon, at startup, then choose Reinstall macOS) replaces system files without erasing your data. It's worth trying only after Safe Mode has ruled out a third-party conflict, since it fixes a narrower class of problems, actual system file corruption, than most Quick Look failures turn out to be.

Fixes: rare, deeper system-file corruption

Symptom → Cause → Fix

If you'd rather jump straight to your exact symptom, use this table as a shortcut.

What you're seeing	Likely cause	Fix
Space bar does nothing at all	File not actually selected, or focus is on the wrong pane	Click the file once first, then press Space
Space bar draws a blue box around the file instead of previewing it	Full Keyboard Access reassigning the space bar	Turn off Full Keyboard Access
Preview window opens but is blank or gray	Corrupted thumbnail cache	qlmanage -r cache
"Preview Not Available" for every file	quicklookd crashed or stuck	qlmanage -r, or relaunch Finder
"Preview Not Available" only for iCloud files	File offloaded to iCloud, not downloaded locally	Click the file to force a download
Preview crashes Finder or spins indefinitely	Conflicting third-party Quick Look extension	Disable extensions one by one, or test in Safe Mode
Only one file type never previews (code, Markdown, etc.)	No extension installed for that format, or a legacy .qlgenerator plugin broken since Sequoia	Install a modern Quick Look extension for that format

Where Quick Folder Preview Fits In

Every fix above is about getting Apple's own Quick Look working the way it's supposed to. None of it changes what Quick Look has never done: preview the contents of a folder, or a Zip or Rar archive, without opening it first. That specific gap is what we're building Quick Folder Preview to close, a drag-and-drop, folder-first take on instant preview for Mac, aimed at macOS 11 and later on both Intel and Apple Silicon.

Honest status

Quick Folder Preview is in development. There's a waitlist, not a download link, and no price has been set. If your immediate problem is Quick Look itself not working, the fixes above solve that today regardless of when anything else ships.

Sources & Further Reading

Full Keyboard Access / space bar conflict: Apple Support Communities thread, macOS 26 Tahoe, related thread on Quick Look and the space bar in Sequoia.

Full Keyboard Access settings, official documentation: Apple Support, Change Keyboard settings for accessibility on Mac.

qlmanage command reference: The Eclectic Light Company, Inside QuickLook previews with qlmanage, A quick look at QuickLook and its problems.

iCloud Optimize Mac Storage and placeholder files: Apple Support, Store files in iCloud Drive on Mac.

Legacy Quick Look plugin (.qlgenerator) support removed in Sequoia: see our own guide to previewing files on Mac for the full breakdown, and our coverage of Homebrew disabling unsigned Quick Look plugin casks for what that means if you installed one through Homebrew.

Frequently Asked Questions

Why is Quick Look not working on my Mac?

Most of the time it's one of three things: quicklookd (the background process that generates previews) has gotten stuck or crashed, the thumbnail cache it reads from is corrupted, or, if pressing Space just draws a blue box around the file instead of opening a preview, Full Keyboard Access has quietly remapped what the space bar does. A relaunch of Finder or a cache reset fixes the first two in under a minute. The keyboard issue needs a different fix entirely, covered below.

How do I fix Quick Look not working on Mac?

Start with the free options in order: relaunch Finder (Option-Control-click the Finder icon in the Dock, then Relaunch), then run `qlmanage -r cache` in Terminal to clear the preview cache. If Space is just selecting the file with a blue outline rather than previewing it, go to System Settings > Accessibility > Keyboard and turn off Full Keyboard Access instead, that's a different bug with a different fix. If nothing previews for any file at all, run `qlmanage -r` to force a full reset of the Quick Look server, then check System Settings > General > Login Items & Extensions for a broken third-party Quick Look extension.

Why does pressing Space just select the file with a blue box instead of previewing it?

This is a known Full Keyboard Access bug that keeps resurfacing across macOS versions, including macOS 26 Tahoe. When Full Keyboard Access is turned on, the system sometimes reassigns the space bar to "activate the focused control" (a selection action) instead of passing it to Quick Look. It isn't your Quick Look installation that's broken. Turn off Full Keyboard Access in System Settings > Accessibility > Keyboard and the space bar goes back to triggering a normal preview immediately, no restart required.

What does qlmanage -r cache actually do?

It clears the Quick Look thumbnail cache, the folder of pre-rendered preview images macOS keeps so it doesn't have to regenerate a preview from scratch every time. If that cache has a corrupted entry, you'll get a blank or gray preview for one specific file, or sometimes for every file of a certain type, until the cache is cleared. It doesn't touch your files, only the cached previews. `qlmanage -r` on its own (no `cache` argument) goes a step further and restarts the Quick Look server itself, rebuilding its list of installed preview plugins, which fixes a wider range of Quick Look failures.

Why won't Quick Look preview files stored in iCloud?

If "Optimize Mac Storage" is on in iCloud Drive settings, macOS offloads files you rarely open to iCloud and leaves a placeholder on your Mac. Quick Look can only preview what's actually on your disk, so a file that hasn't finished downloading shows "Preview Not Available" even though Finder displays its name and icon normally. Click the file once to trigger the download (look for the cloud-with-down-arrow badge on its icon), wait for it to finish, then try Quick Look again.

Does reinstalling macOS actually fix Quick Look?

Rarely, and it should be close to the last resort, not an early step. Reinstalling macOS through Recovery Mode without erasing your disk replaces system files, which can fix Quick Look if a system file itself is corrupted, but that's an uncommon cause next to a stuck process, a bad cache, a Full Keyboard Access conflict, or a broken third-party extension. Try Safe Mode first: if Quick Look works normally there, a third-party extension is the real culprit and reinstalling macOS won't be necessary at all.

Is quicklookd a virus?

No. quicklookd (and its companion processes, QuickLookUIService and com.apple.quicklook.ThumbnailsAgent) are Apple's own built-in macOS processes that generate every Quick Look preview and Finder thumbnail you see. Seeing them in Activity Monitor, including using noticeable CPU briefly while previewing large or complex files, is completely normal. Force-quitting them is a legitimate, safe troubleshooting step; macOS relaunches them automatically the next time you trigger a preview.

Will a future macOS update fix these bugs automatically?

Possibly, but not on a guaranteed timeline. Apple has quietly patched specific Quick Look regressions in point releases before, and the Full Keyboard Access spacebar bug has been reported on and off since Monterey, so it isn't new to Tahoe and hasn't been permanently fixed yet. Keeping macOS updated (System Settings > General > Software Update) is worth doing regardless, but don't wait on an update when the fixes above take under a minute each.

The Bottom Line

Quick Look failures almost always trace back to one of a handful of causes, not some deep, unfixable system problem. Relaunching Finder and clearing the cache resolves most of them in under a minute. If the symptom is specifically a blue selection box where a preview should be, don't waste time on cache resets at all: go straight to Full Keyboard Access, since that bug has nothing to do with quicklookd and everything to do with a keyboard accessibility setting reassigning what Space does. Work through the list in order, and reinstalling macOS should be the very last thing you try, not the first.

Looking for more Mac productivity guides? Read our full guide to previewing files on Mac without opening them, browse every 1dot.ai guide, or check Quick Folder Preview's product page for the waitlist.

Want Folder and Archive Previews Without Extracting?

Quick Folder Preview is in development: a drag-and-drop, folder-first take on instant preview for Mac. No price or release date set yet, just a waitlist.

Join the Waitlist Read More Guides