# Can I Delete Previews.lrdata? Too much for a new iMac with an SSD.



## CameraCarl

I just bought a new iMac with a 512GB SSD instead of a 1TB Fusion drive, so I need to start being more cautious about storage.  When starting to move Lightroom Classic CC to my new computer, I noticed that I have a huge LR preview data file.  I have almost 350GB of data in my Lightroom Catalog Previews.lrdata file. In the past I made lots of 1:1 previews thinking it would speed up my image reviews during the culling process in the Library module and when moving from one image to the next in the Develop module.  In the future, I will have to be more careful. 

But the key question right now is what do I do with the lrdata file as I migrate Lightroom to my new computer?  Do I simply _not_ move the lrdata files over? Or move them knowing they will almost completely fill my internal desktop storage, then immediately delete all the previews? Or something else?


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## clee01l

The images that you see when you run LR are from "Previews.lrdata" It is a necessary folder for LR to operate.    You can delete it, but LR will build it back up as it needs to generate previews for each file that you use in LR.   With your limited primary drive, you better option is to move all of your master images to an external HD (EHD)   If you still have limited space on your primary drive, then move the folder containing the LR catalog and "Previews.lrdata" to the EHD as well.  "Smart Previews.lrdata" is a folder that can be deleted and  if you instruct LR to not build smart previews, it won't be recreated.
In every case you need to leave ~100GB of that 512GB free so that LR and other apps can have a space to create temporary files during processing.   Running out of free space will cause the systems and apps like LR to slow down.


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## David Gibson

clee01l said:


> The images that you see when you run LR are from "Previews.lrdata" It is a necessary folder for LR to operate. You can delete it, but LR will build it back up as it need to generate previews for each file that you use in LR. With your limited primary drive, you better option is to move all of your master images to an external HD (EHD) If you still have limited space on your primary drive, then move the folder containing the LR catalog and "Previews.lrdata" to the EHD as well. "Smart Previews.lrdata" is a folder that can be deleted and instruct LR to not build smart previews.
> In every case you need to leave ~100GB of that 512GB free so that LR and other apps can have a space to create temporary files during processing. Running out of free space will cause the systems and apps like LR to slow down.



That’s what I do and it works well. I keep my most recent work on the laptop drive and then migrate to external drive once finished. 


Sent from my iPhone using Tapatalk


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## Paul McFarlane

Just to add a lot of my work (for Clients) is transient, so I tend to delete the Previews file periodically and just build for the folders needed, keeps space tighter and the previews for a lot of the older work I do are simply irrelevant (and can be built again anyway)

Only other benefit in keeping them is if something catastrophic happens to your originals then smaller JPG's can be built from the previews - but a decent backup routine takes care of that


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## prbimages

Also worth noting - you can set an option in the _Catalog Settings -> File Handling_ tab to automatically discard 1:1 previews after a specified time period (a day, a week, a month, never). Set this to a short time period and it will keep your preview storage requirements to a minimum.


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## CameraCarl

CameraCarl said:


> I just bought a new iMac with a 512GB SSD instead of a 1TB Fusion drive, so I need to start being more cautious about storage.  When starting to move Lightroom Classic CC to my new computer, I noticed that I have a huge LR preview data file.  I have almost 350GB of data in my Lightroom Catalog Previews.lrdata file. In the past I made lots of 1:1 previews thinking it would speed up my image reviews during the culling process in the Library module and when moving from one image to the next in the Develop module.  In the future, I will have to be more careful.
> 
> But the key question right now is what do I do with the lrdata file as I migrate Lightroom to my new computer?  Do I simply _not_ move the lrdata files over? Or move them knowing they will almost completely fill my internal desktop storage, then immediately delete all the previews? Or something else?





clee01l said:


> The images that you see when you run LR are from "Previews.lrdata" It is a necessary folder for LR to operate.    You can delete it, but LR will build it back up as it needs to generate previews for each file that you use in LR.   With your limited primary drive, you better option is to move all of your master images to an external HD (EHD)   If you still have limited space on your primary drive, then move the folder containing the LR catalog and "Previews.lrdata" to the EHD as well.  "Smart Previews.lrdata" is a folder that can be deleted and  if you instruct LR to not build smart previews, it won't be recreated.
> In every case you need to leave ~100GB of that 512GB free so that LR and other apps can have a space to create temporary files during processing.   Running out of free space will cause the systems and apps like LR to slow down.


I'm coming back to this thread since my Previews.lrdata file has again grown to 139GB.  When I first asked the question, I was moving the Lightroom catalog to a new computer. The previews file size had remained manageably small until recently when I found it was causing my 512GB drive to slow down. So I tried deleting the entire Lightroom Catalog Preivews.lrdata file.  Not surprisingly, all of my previews are gone, and I presume Lightroom will start building new previews. So after this rash action, I am wondering:
1. Did I make a big mistake? (If so I made a copy of the lrdata file on another drive  and can always put it back where it came from) 
2. With a catalog of about 240,000 images, how long will it take Lightroom to build previews?
3. Is there a way to build the previews I need the most first?
4. Is there some way to maintain a catalog as large as mine is on the internal 512GB SSD since I assume that the previews created will be stored with the catalog on the SSD and will continue to grow in the future? Or should I move the catalog to an external drive? And if I do what downside is there?

iMac mid-2017. OS 10.13.6
LR Classic CC version 8.2.1


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## Johan Elzenga

Lightroom only rebuilds those previews that it needs to show you images. So how many are rebuilt depends entirely on how many you view, in the grid and in loupe view.


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## Dan Marchant

CameraCarl said:


> 4. Is there some way to maintain a catalog as large as mine is on the internal 512GB SSD since I assume that the previews created will be stored with the catalog on the SSD and will continue to grow in the future? Or should I move the catalog to an external drive? And if I do what downside is there?


1. _Edit > Catalog Settings > File Handling_ - What settings do you have for previews? Higher quality = bigger files. Also how long are 1:1 previews retained? If they are never deleted they will fill up the drive.

2. The catalog (and previews) should really be on your fastest HD for performance reasons.


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