max size of the photos library

Does the program run just as well at 500GB size as it does At let say 4TB

As I recall the limit on photos in a library is 1,000,000. The size will depend on the size of the image files.

It's safe to say the larger library will run slower than a smaller one since there are many more image files to process an manage.

The speed of managing a large library is dependent on the CPU speed, amount of RAM, amount of free space on the volume where the library is located, whether the volume is on an SSD or slow HDD drive.

Having the library on a SSD will improve its speed and response time for any operation that you may be performing. However, it may not be that much different depending on whether the library has finished it's background processing or not. For example, a 51,000 library on an external HDD opens fully in 6 seconds. A 7,000 library on my SSD opens in 2 seconds. Both times are very quick.

I also keep a minimum of 20GB of free space for system and application performance.

So how big can it be? When should I consider splitting it up into different libraries.

When the library is filling half of the capacity of your drive. You will need working space, if the library ever needs repairing or upgrading to a new version.

Photos is supposed to be able to open Aperture Libraries or iPhoto Libraries, so you should be able to have at least one million photos or videos in your library.

No limit except available disk space

LN

I've never tried a library that size.

You will probably not notice the size of the library when editing photos, but the regular maintenance may become problematic - updating the library to new versions, copying to a new drive, making backup copies. Then the whole library will have to be processed, and maybe a new scan for faces or categories will need a very long time.

PowerPhotos os a very versatile third-party application, the successor to iPhoto Library Manager.

https://www.fatcatsoftware.com/powerphotos/

The free trial version lets you browse your Photos Library in a second window in a very convenient way - with the filename or the titles below the thumbnails, or in a column view, where you can sort the the photos by file size or the filename, etc.

The full, paid version can search for duplicates or merge libraries, or move albums and photos between libraries.

Launching PowerPhotos for a large library takes a long time, the larger the library is, the longer it will take. I simply launch Power Photos once and never close it.

No Idea - My libraries are not that large - pretty much reports are that size is not a big issue for Photos but number of smart albums is and if you use PowerPhotos size is an issue

LN