Share library on external drive between two Mac computers

One important issue to be aware of if subscribing.

For computer users, their is Lightroom Ecosystem (Cloud Based) Lr, and Lightroom Classic LrC. Do not confuse one with the other. What you are used to is now called Lightroom Classic

If you decide to subscribe, their are several plans, one that users accidentally subscribe to, and then get very unhappy with is the Lightroom Plan. That plan only includes Lightroom Ecosystem (Cloud Based) Lr.

Their is no plan with only Lightroom Classic LrC. Most users wanting Lightroom Classic will subscribe to thePhotography Plan. That plan includes PS, Lr, Lrc, Bridge, and misc.

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It should work, as long as the Lightroom Classic catalog folder and the images it references are all stored on that external volume.

Be aware that, like many Mac apps, Lightroom Classic settings, presets, templates, and so on are stored in a folder within the hidden Library folder inside each user account’s macOS home folder. So the defaults and preferences/settings will not travel with the catalog and may differ among users. (Some Lightroom Classic settings can be set to be stored with the catalog instead, and in your case, they should be.)

I haven't had experience of LR in many years…want to store the LR Library on an external hard drive that can be moved/shared between the two. (I have no interest in the Cloud.)…I did download a trial of LR to both computers about a month ago…

By @Patrick34120243woms

Just to be sure, your goal can be accomplished with Lightroom Classic (today’s name for the traditional version that stores all originals only locally), but your post uses the name “Lightroom” (Adobe chose to apply that name to the newer version that stores all originals only in the cloud). Be sure you download, install, and use Lightroom Classic, not Lightroom, if you want to ensure that your originals are stored only on a local file system.

As to the import, do it in stages if there are a lot of images. I'd have them all in place on the drive and then use Add in import to get them in. 

With Lightroom Classic, you just store the images and catalog on the external drive. Always close Lightroom Classic before ejecting. Double click on the .lrcat file on the drive to open it into Lightroom Classic on the computer. Lightroom should remember this after the first run, but if you open Lightroom without the drive connected, it may create a new catalog. Double clicking the drive catalog ensure you have the right one.