How do I make Photos keep files on drive and not import onto computer?

The Apple Photos Library was not designed to have image files on an external server or hard drive and just be referenced. That is called a "referenced library". If the library is launched at any time without the volume/server connected it will lose all its links to the original image files.

You have have a managed library on an external volume that's been formatted APFS or Mac OS Extended (journaled) but not on a server as the server's operating system will be incompatible with the Photos library.

Some have run a reference library on a local volume but have eventually ended up with a damaged and unusable library.

There are other apps that can have the original files on an external volume or server. I'm not familiar with them but any of the DAM (Digital Asset Management) apps should work.

Have you considered using Infinity Photos or Photoshop Elements for Mac (both are a one time purchase)? I have PSE 2025 on my Mac Mini and the only thing it doesn't have that Photoshop has is the ability to manage, edit and save as CMYK color format. If it need that I'll use GraphicConverter to do the conversion.

Photos does lots of work in the background, and networked drives interfere with that. You could add a cable connected external drive to your system, independent of the NAS, and store a Photos Library, there.

You mention iCloud, but I take it that you don't use that service. iCloud has lots of software infrastructure to allow operation over the internet. But iCloud, too, can be a problem if the drive is plugged and unplugged during background processes.

As Old Toad said, in Photos the pictures need to be copied into the Library, itself-- a managed Library. I keep my originals archived, but Photos is a non-destructive editor, and the originals in its Library remain untouched (except for their filenames.)

pirhan wrote:

Well that's a bummer. I was looking forward to using Photos as it plays the mp4 videos where as Lightroom 5 does not. The interface was nice too. My laptop hard drive is 500GB and I have more than 500GB of photos/videos so I need to house the files elsewhere. That's a huge shame that the developers didn't design it like that.... weird since I saw Cloud service available with Photos and that's offsite?

Well, you get what you pay for and Photos is a freebie that comes with each Mac. The iCloud library is on Apple's servers which are formatted to be compatible with a Photos Library. NAS servers have a different operating system which are not compatible with a Photos library.

"I don't think Photos works in the background if it's not open?"

Richard.Taylor is not talking about background *processes* - though Photos does do some of that when analyzing images - he means more "behind the scenes" : Photos is a lot more than just a viewing program and keeps track of all sorts of things in its database. In fact, just the fact that it *has* a database probably makes it unsuitable for what you want to do.