When Lightroom is taking up space on a Mac, the usual culprit is Lightroom Classic's preview file, Previews.lrdata, which sits next to your catalog in Pictures › Lightroom. It holds the thumbnails and larger previews you see as you browse, and full-size 1:1 previews can make it very large.
You can clear it. With Lightroom Classic quit, Previews.lrdata can go to the Trash, and Lightroom Classic rebuilds previews as you open folders again, more slowly at first. The catch: it needs the original photos to do that, so photos on a disconnected drive show no preview until the drive is back.
Three smaller items are worth checking too: old catalog backups, which pile up in a Backups folder, and the Camera Raw and video caches, which Lightroom Classic's own preferences can purge. Smart Previews are a separate file and serve a different purpose.
What you should never delete is the catalog itself, its .lrcat-data file, and above all your original photos. They're the only parts Lightroom Classic can't rebuild.
What Lightroom Classic keeps on your Mac
Lightroom Classic doesn't store your photos inside the app. Adobe describes the catalog as a database that tracks where your photos are and everything you've done to them, while the photo files themselves stay where you imported them.
Around that catalog, Lightroom Classic keeps several files of its own. Some are your work; some are rebuilt whenever they're missing.
Where is the Lightroom folder on a Mac?
By default, Adobe says, catalogs live in ~/, with the catalog named Lightroom Catalog.lrcat. A catalog you create yourself gets a folder of its own, named like the catalog.
To find the catalog you're actually using, choose Lightroom Classic › Catalog Settings, open the General panel, and click Show in the Information area. Finder opens the catalog's folder.
Which files are in the catalog folder?
Adobe's file locations page lists the defaults. Each starts with the catalog's name:
| File | What it is | Rebuilt if removed? |
|---|---|---|
Lightroom Catalog.lrcat | The catalog: edits, ratings, keywords, collections | No |
Lightroom Catalog.lrcat-data | More catalog data, including AI edits | No |
Lightroom Catalog Previews.lrdata | Thumbnails, standard and 1:1 previews | Yes, from the originals |
Lightroom Catalog Smart Previews.lrdata | Small editable copies for offline work | Only if you build them again |
Lightroom Catalog Helper.lrdata | Not documented by Adobe | Leave it |
Backups | Copies of the catalog | No; they're backups |
.lrcat.lock and .lrcat-journal | Used while the catalog is open | Never remove them by hand |
How do you see what's using the space?
Open the catalog's folder in Finder and choose View › as List. Then choose View › Show View Options and turn on Calculate all sizes, so folders and packages show their real size. Sort by Size.
For one item, select it and choose File › Get Info. Previews.lrdata is a package, so Get Info is the quickest way to see how much it holds.
Why does the Lightroom folder get so big?
Mostly because of previews. Every photo you browse gets a thumbnail and a standard preview, and every photo you zoom into at 100% gets a 1:1 preview. On a catalog of tens of thousands of raw files, that adds up.
Backups add more over time, since each one is a full copy of the catalog. The catalog file itself grows with your edits, but it's rarely the biggest item.
Previews.lrdata: the file you can clear
The catalog's entry for Lightroom Classic previews rates this file Usually safe. It's rebuilt by Lightroom Classic, so nothing is lost, but there's a cost while it's rebuilt and a condition for rebuilding at all.
What's inside Previews.lrdata?
Adobe says the file holds your thumbnails, small previews and 1:1, full-size previews. It's what lets Lightroom Classic show a grid of thousands of photos without opening every raw file each time.
On a Mac it looks like a single file, but it's a package. Don't open it and remove pieces; Adobe's Mac steps treat it as one item.
Is it safe to delete Previews.lrdata?
Yes, under two conditions. Lightroom Classic must be quit, and the file's name must match a catalog. Adobe's catalog page says a previews file is safe to delete as long as its name matches the .lrcat file, and that Lightroom Classic regenerates it, running more slowly until previews are rebuilt.
The rule's side effects add the condition that matters most. Folders open more slowly while previews are rebuilt, and photos whose originals are on a disconnected drive can't show previews until that drive is connected again.
What happens to photos you've archived?
Adobe's performance guide spells it out: if your catalog holds previews of photos you've archived elsewhere, deleting Previews.lrdata deletes those previews too. Lightroom Classic can only rebuild a preview from the original.
So if you keep older shoots on a drive that's usually in a drawer, connect it before you browse those folders again. Or keep Smart Previews for them, described below.
How to delete Previews.lrdata
Adobe's steps for a Mac:
- Quit Lightroom Classic.
- In Finder, open the folder that contains your catalog, by default
~/.Pictures/ Lightroom - Drag the file named after your catalog and ending in Previews.lrdata to the Trash.
- Open Lightroom Classic again.
Leave the file ending in Smart Previews.lrdata alone unless you mean to remove Smart Previews too. Adobe says it's different from previews and doesn't need deleting. The file stays in the Trash, where File › Put Back returns it, until you empty the Trash.
When is deleting it the right move?
Adobe lists three situations: your disk gets unexpectedly full, Lightroom Classic shows an error about its preview cache, or photos display with artifacts such as coloured lines, dots or patches. For the last two, Adobe says deleting the file is the fix.
For space alone, try the gentler options in the next section first. They shrink the file without throwing away every standard preview.
1:1 previews, standard previews and Smart Previews
Lightroom Classic makes several kinds of preview. Knowing which is which tells you what to trim and what to keep.
What are 1:1 previews?
Adobe describes 1:1 previews as a 100% view of the actual pixels, rendered by the Camera Raw engine. Lightroom Classic uses them whenever you zoom to 1:1 or more in the Library module, and makes them on import if you choose Render Previews › 1:1.
They're the largest previews by far, which is why Adobe gives you a way to discard them automatically.
How do you discard 1:1 previews automatically?
- Choose Lightroom Classic › Catalog Settings.
- Click File Handling.
- Set Automatically Discard 1:1 Previews to a shorter period.
Adobe's options run from a day to a month, or never. It notes that with Never or After 30 Days, Previews.lrdata can grow very large, taking many gigabytes, and that each time 1:1 previews are discarded, Lightroom Classic has to make them again when you zoom in.
Which setting should you choose?
It's a trade between disk space and waiting. Adobe's performance advice is to keep 1:1 previews as long as space allows, since remaking them takes time. If space is tight, a week is a fair middle ground: recent shoots stay quick, and older ones give the space back.
Can you clear previews from inside Lightroom Classic?
Yes, from the Library › Previews menu. Adobe's performance guide says to choose Discard Standard and 1:1 Previews for the selected photos. Select the folders or shoots you're done with in Grid view first, so only their previews go.
This is the targeted alternative to deleting Previews.lrdata. Lightroom Classic makes previews again the next time you open those photos, provided the originals are connected.
Which previews should you render on import?
The import window's File Handling panel offers Minimal, Embedded & Sidecar, Standard and 1:1 under Render Previews. Adobe says 1:1 on import makes Lightroom Classic more responsive later, at the cost of a slower import and more space.
If space matters more than speed, choose Standard. Lightroom Classic still makes 1:1 previews for the photos you zoom into, and only those.
Keep standard previews no larger than you need
Standard previews are made for every photo you browse, so their size matters. In Catalog Settings › File Handling, Adobe suggests a Standard Preview Size closest to the longest edge of your screen, but not smaller, and a Preview Quality of Low or Medium.
A smaller size and quality keeps Previews.lrdata smaller from now on. Existing previews keep their old size until they're made again.
Smart Previews: small copies for editing offline
Smart Previews are lightweight files in a lossy DNG format, kept in a separate Smart Previews.lrdata file next to the catalog. They let you edit photos whose originals are on a drive that isn't connected, and the edits apply to the originals when the drive comes back.
Adobe's own example shows the scale: 500 raw files from a high-end camera took 14 GB, while their Smart Previews took 400 MB.
- The original raw files14 GB · Review first
- Their Smart Previews0.4 GB
Adobe's figures from its Smart Previews help page. Your sizes depend on the camera and the files.
When should you discard Smart Previews?
When you no longer need to edit those photos away from their drive. Choose Library › Previews › Discard Smart Previews, or click Original + Smart Preview below the histogram and choose Discard Smart Preview for one photo. Your originals aren't touched.
Smart Previews can also save space the other way round. Build them for photos you're moving to an external drive, and you can keep working on those photos with the drive unplugged.
| Preview | Size | Made when | How to trim it |
|---|---|---|---|
| Thumbnails and standard | Small to medium | You browse | Smaller size and quality in Catalog Settings |
| 1:1 | Large | You zoom to 100%, or on import | Automatically Discard 1:1 Previews, or the Library menu |
| Smart Previews | Small | You build them | Discard Smart Previews |
| All of Previews.lrdata | Everything above but Smart | Rebuilt as you browse | Trash the file with Lightroom Classic quit |
The Camera Raw cache and the video cache
Two caches live outside the catalog folder, in your Library. Both are capped or controlled by Lightroom Classic's preferences, and both are rebuilt on demand.
What is the Camera Raw cache?
When you edit a raw photo in the Develop module, Lightroom Classic renders it from the original data. Adobe says the Camera Raw cache keeps that early-stage data so later previews of the same photo are faster, and that the cache is used only by the Develop module.
Adobe sets its maximum size to 5 GB by default. It's a cap, so the cache doesn't grow past what you set.
How do you purge or resize it?
- Choose Lightroom Classic › Settings or Preferences, depending on your version.
- Open Performance. Adobe's preferences page lists Camera Raw Cache Settings there; older versions keep them in File Handling.
- Click Purge Cache to empty it, change Maximum Size, or click Choose to move it to another folder or drive.
Adobe suggests purging it when deleting Previews.lrdata hasn't fixed artifacts in your photos. For space, lowering the maximum size has a lasting effect, while a purge only lasts until you edit again.
Is a bigger cache better?
For speed, Adobe says yes. It notes that some users raise the cache to 20 GB or more and find the Develop module much faster. So this is one cache where giving space back has a real cost in waiting.
- Default maximum5 GB · Safe
- What some users set for speed20 GB · Safe
Both figures are from Adobe's Optimize Lightroom performance page. The cache never grows past the maximum you set.
Where is the video cache?
Lightroom Classic's preferences also have Video Cache Settings, which Adobe says stores video data so previews of videos generate faster. Adobe's video troubleshooting page puts it in ~/, in folders named Media Cache and Media Cache Files.
That page lists removing those two folders, with Lightroom Classic quit, as a step for video playback problems. If you don't import video, there's little or nothing there.
Is it the same as Premiere Pro's media cache?
No, though the folder names match. Premiere Pro, After Effects and Media Encoder keep their own media cache in ~/, which the catalog's Adobe media cache entry covers. Lightroom Classic's is in your Caches folder.
Both are rebuilt when needed. Your Caches folder as a whole is rated Safe in the catalog's user caches entry, and the post on whether ~/Library/Caches is safe to delete explains what that means.
| Cache | Default location | Size | Control |
|---|---|---|---|
| Camera Raw cache | Your Caches folder, shown in its settings | Capped, 5 GB by default | Performance › Purge Cache |
| Video cache | ~/Library/Caches/Adobe/Lightroom/Video | Grows with video use | Video Cache Settings |
| Premiere Pro media cache | ~/Library/Application Support/Adobe/Common | Grows per project | Premiere Pro's settings |
Catalog backups piling up
Lightroom Classic offers to back up the catalog when you quit, and each backup is a full copy. Over a few years they can take more space than the catalog itself, and nothing removes them for you.
Where are Lightroom Classic's backups?
Adobe says backups go into a Backups folder next to the catalog, by default ~/ for the default catalog. Inside are folders named with the date and time of each backup, such as 2026-10-26 1830, each holding a copy of the catalog.
Recent versions save each backup as a zip file. Adobe's restore steps start with unzipping it. The Backup Folder in the backup dialog shows exactly where yours go.
Which backups should you keep?
Adobe's own advice is to delete or compress old backups to save space, because Lightroom Classic writes a new catalog every time it backs up. A sensible set to keep:
- the most recent few, in case the catalog breaks or you undo a big mistake
- one from before each major Lightroom Classic upgrade, since newer catalogs can't be opened by older versions
- one copy somewhere other than the Mac's own disk, as Adobe recommends
Everything older than that is a copy of a catalog you've replaced many times over.
How do you delete old backups in Lightroom Classic?
Since version 14.2, released in February 2025, Lightroom Classic manages backups itself. Choose Lightroom Classic › Catalog Settings, open Backups, and you'll see every backup sorted by date, with Show, Delete and Remove.
Adobe says Delete removes backups from the disk, while Remove only takes them off the list. Command-click to select several. Adobe doesn't say whether Delete uses the Trash, so if you want an undo, click Show and move old backup folders to the Trash in Finder instead.
Can you keep backups on another drive?
Yes. In the backup dialog that appears when you quit, click Choose next to Backup Folder and pick a folder on an external drive. Adobe recommends a separate disk for backups anyway, and it moves their space off your Mac.
Remember that a catalog backup isn't a photo backup. Adobe is explicit that it includes only the catalog, so your photos need their own backup, such as Time Machine.
Old catalogs you no longer use
Adobe doesn't recommend using several catalogs, but many Macs have a few: one per year, a test catalog, a copy from an old Mac. Each has its own previews file and its own backups.
If you've merged an old catalog into your main one with File › Import From Another Catalog, its previews file can go. Deleting the catalog itself is a bigger step: Adobe says it erases all the work not saved in the photo files, while the photos stay.
Old catalogs left by upgrades
When a new version of Lightroom Classic upgrades your catalog, Adobe says it first creates a compressed copy of the old one in the catalog folder. Once you're sure the upgraded catalog works, older copies from previous versions are candidates to archive or remove.
Check the file names and dates before you do. The catalog you open every day is the one Show in Catalog Settings points to; leave that one, and its .lrcat-data file, exactly where they are.
What you should never delete
Some files in and around the catalog folder look technical and expendable. They aren't.
The catalog and its .lrcat-data file
The .lrcat file holds every edit, rating, keyword and collection. Adobe says the .lrcat-data file next to it, added in Lightroom Classic 11, holds important information about your photos and edits, and that without it, AI edits are lost for good. Back up both together.
Lock and journal files
A .lrcat.lock file stops the catalog from being overwritten while it's open, and Adobe says a .lrcat-journal file is used to check for incomplete records. Adobe's instruction is not to delete the journal file unless you're deleting its catalog too.
Helper.lrdata
Many catalog folders have a file ending in Helper.lrdata. Adobe doesn't document it on its file locations page, so there's no official statement of what it holds or whether it's rebuilt. It isn't where your space is; leave it alone.
Your original photos
They're the only part of a Lightroom Classic setup that nothing can recreate. Previews, caches and even the catalog's speed tricks all depend on them. Before you delete any photo to save space, make sure it's a true duplicate or a reject you won't miss.
Duplicates are common in photo libraries, especially after several imports from the same cards. The post on finding duplicate photos on a Mac covers how to find them safely, and inside Lightroom Classic, removing a photo from the catalog is a different action from deleting the file.
Can you compress raw files to save space?
Not in the way you'd zip a folder you're done with. A zipped raw file can't be browsed or edited until it's unzipped. For finished archives you rarely open, the post on compressing files on a Mac explains what compression saves and where it doesn't help.
Moving the catalog or photos to an external drive
When the internal disk is too small for a growing library, moving photos to an external drive frees the most space by far. The key is to move them in a way the catalog follows.
How do you move photos the supported way?
Adobe's advice is to move photos and folders from inside Lightroom Classic, so the catalog keeps track:
- Connect the external drive.
- In the Library module's Folders panel, click the plus button and choose Add Folder.
- Choose a folder on the external drive, or click New Folder to make one, then click Choose.
- Drag folders from the internal drive onto the new folder in the Folders panel.
Adobe says changes made in the Folders panel apply to the folders on the disk, so the files really move. Lightroom Classic can't copy folders, only move them.
What if you already moved photos in Finder?
Then the catalog loses track, and Adobe says a question mark appears on the folder in the Folders panel. Control-click the folder, choose Find Missing Folder, and point it to the new location.
If you copied a folder to the external drive and want Lightroom Classic to use the copy, Control-click the original folder and choose Update Folder Location. Once the photos show up from the new place, the internal copy can go to the Trash.
Can you move the catalog too?
Yes, though it frees less space. Adobe's steps: back up first, find the catalog with Show in Catalog Settings, quit Lightroom Classic, then move the .lrcat, .lrcat-data, Previews.lrdata and Smart Previews.lrdata files together in Finder. Double-click the .lrcat file in its new place to open it.
Adobe says catalogs can't be stored on network drives, though photos can. It also recommends keeping the preview file in the same folder as the catalog; if they're separated, Lightroom Classic has to regenerate the previews.
Working with photos on an external drive
With the drive unplugged, Lightroom Classic still shows previews it has already made, and Smart Previews let you edit. Photos with neither show only what's in the preview file, and can't be rebuilt until the drive is back.
That's why deleting Previews.lrdata and moving photos to an external drive don't mix well. Do one, then let Lightroom Classic finish rebuilding before you unplug the drive.
Time Machine and Lightroom Classic
Adobe recommends not running a Time Machine backup or restore while Lightroom Classic is in use. Quit it before a backup you start yourself. The Photos app has a similar rule about its library, covered in the post on moving a Photos library to an external drive.
Lightroom vs Lightroom Classic
Adobe makes two apps with Lightroom in the name, and they store photos in completely different ways. Check which one you have before you go looking for Previews.lrdata.
How does Lightroom (the cloud app) use space?
Lightroom keeps your originals in Adobe's cloud and manages a local cache on the Mac. Adobe says its Cache preferences show how much space its database, thumbnails and cached photos use, and let you set a cache size limit.
You can also choose Store A Copy Of All Smart Previews Locally, or change the Storage Location For Originals to another drive. Lowering the cache limit is the supported way to shrink it, since originals stay in the cloud.
And when Lightroom Classic syncs with the cloud?
Lightroom Classic can sync photos with Lightroom's cloud. Adobe warns not to keep the catalog, or the folder Lightroom Classic uses for synced images, inside a folder that iCloud Drive or OneDrive syncs, because that can use up their online storage.
If you've stopped syncing, Lightroom Classic's preferences offer Delete All Synced Data, which Adobe says removes the synced data from Creative Cloud while your original photos on the Mac stay untouched.
| Lightroom Classic | Lightroom | |
|---|---|---|
| Where originals live | Wherever you imported them | Adobe's cloud, plus a local cache |
| What grows on the Mac | Previews, backups, caches | The cache, up to its limit |
| How to shrink it | The steps in this post | Lower the cache size limit |
| What's irreplaceable locally | Originals and the catalog | Originals not yet uploaded |
What doesn't help, and mistakes to avoid
Clearing caches won't make Lightroom Classic faster
Deleting previews and purging caches frees space. It doesn't speed Lightroom Classic up; for a while it does the opposite, while everything is rendered again. Adobe's performance advice runs the other way: keep previews longer and give the Camera Raw cache more room, as long as your disk has space.
What Adobe does recommend for speed is free space itself. Its performance page asks you to keep at least 20% of the drive that holds your catalog, previews and photos free.
Moving or renaming photos in Finder
The catalog stores where each photo is. Move a folder in Finder and Lightroom Classic loses it. Use the Folders panel, or reconnect with Find Missing Folder afterwards.
Deleting previews when originals are offline
If your originals are on a drive you rarely connect, deleting Previews.lrdata leaves those photos without previews until you connect it. Connect the drive first, or build Smart Previews for the photos you want to keep editing.
Other mistakes to avoid
- Trashing the whole Lightroom folder. It holds the catalog and its backups, not just previews.
- Deleting the Smart Previews file by accident. Its name looks like the previews file's; read the whole name.
- Keeping every backup forever. Adobe suggests deleting or compressing old ones.
- Keeping backups only on the same disk. A failed disk takes the catalog and its backups together.
- Deleting originals because Lightroom Classic shows a preview. A preview is a picture of the photo, not the photo.
- Emptying the Trash at once. Until it's emptied, File › Put Back undoes a mistake.
Where else photo and video apps keep rebuilt files
Video editors have their own version of previews: render files, proxies and optimized media. The post on iMovie and Final Cut Pro render files explains how to clear those with the apps' own commands.
If you're leaving Adobe altogether, the post on uninstalling Adobe Creative Cloud on a Mac covers what to keep first, catalogs and presets included.
For Apple's own photo app, everything lives inside the Photos library and is managed by Photos. The post on what's in the Photos library explains how to shrink it with Photos' own settings.
How the app does it
Wombit scans the whole disk or any folder and explains every item in plain language, reading only names, sizes and dates. File names and paths never leave your Mac.
A Previews.lrdata file next to its catalog in Pictures › Lightroom shows up on the map with its real size, explained from the catalog's entry: what it holds, that Lightroom Classic rebuilds it, and that it needs the originals to do so. The catalog, its Smart Previews and its backups aren't part of that entry.
Lightroom Classic's previews are Usually safe, so they never start checked in Cleanup and don't count toward the safe total. Folders in your Caches folder, such as Adobe's, which holds Lightroom Classic's video cache, are Safe.
~/
Pictures/ Lightroom/ * Previews.lrdata Thumbnails and previews that Lightroom Classic renders so it can show your photos quickly.
Usually safe · Moves it to the Trash
~/
Library/ Caches/ * Data that apps and macOS services keep so they can load things faster. Apps create it again when they need it.
Safe · Moves it to the Trash
Items whose app is open are left out, and the review sheet offers to quit the app the way ⌘Q does. Everything goes to the Trash, where Undo and Put Back work.
The scan, the map and the explanations are free. Cleanup is PRO, one $4.99 payment with lifetime access. Every Pro tool's review is free to open, so you see what would go and why before you buy.
Frequently asked questions
Is it safe to delete Previews.lrdata?
Yes, with Lightroom Classic quit, as long as the name matches your catalog's. Adobe says Lightroom Classic rebuilds previews as you open folders, so browsing is slower for a while. Photos whose originals are on a disconnected drive show no preview until the drive is back, so connect it first.
Why is my Lightroom Previews.lrdata file so big?
Usually 1:1 previews. They're full-size renders, and if Automatically Discard 1:1 Previews is set to Never or After 30 Days, Adobe says the file can grow to many gigabytes. Set a shorter discard time in Catalog Settings › File Handling, or delete the file and let Lightroom rebuild it.
Can I delete old Lightroom catalog backups?
Yes. Adobe says Lightroom Classic writes a new catalog every time it backs up and suggests deleting or compressing old backups to save space. Keep the most recent few, plus one from before a major upgrade, ideally on another drive. Lightroom Classic 14.2 and later can delete them from Catalog Settings › Backups.
Does clearing the Camera Raw cache free much space?
Only up to its maximum size, which Adobe sets to 5 GB by default. Purge it from Lightroom Classic's preferences when it misbehaves or you need the space. Adobe actually suggests a larger cache for faster editing in the Develop module.
Will deleting Smart Previews delete my photos?
No. Smart Previews are small copies in a separate Smart Previews.lrdata file, used to edit when originals are offline. Discarding them leaves your originals alone, but you lose the ability to edit photos whose drive isn't connected.
How do I move Lightroom Classic photos to an external drive?
Do it inside Lightroom Classic so the catalog keeps track. Add a folder on the external drive with the plus button in the Folders panel, then drag folders into it. If you move photos in Finder instead, use Find Missing Folder to reconnect them.
Does Lightroom (not Classic) use the same files?
No. Lightroom stores originals in Adobe's cloud and keeps a local cache whose size you set in its Cache preferences. Lightroom Classic keeps a catalog and previews next to it and leaves your originals wherever you imported them.