I use Mac computer and have the lightroom catalogue on an external drive. Also on this drive are some lighroom libraries. The drive is now full and when I try to open Lightroom, it states that there is not enough room. My question is ; Can I move the catalogue to another drive or Mac and so allow me to open the Lightroom app. Not sure if this is the answer.
Please show the exact message before you do anything else. Post a screenshot, or write it here word by word.
What do you mean "Please show the exact message before you do anything else. Post a screenshot, or write it here word by word".
I thought the question was self explanitory
"Word-for-word" is self explanatory. But if you want advice on what to do, providing the requested information is required.
The reason I asked to see the exact wording is because the catalog would normally not need so much extra space all of a sudden that such a message is expected. It looks like your external drive is filled to the brim however, if there isn't even enough room for as little as 20 MB.
Yes, you can move the catalog to another drive. Just drag and drop the entire catalog folder. Then launch Lightroom by double clicking the catalog file in the new location. From now on Lightroom should remember where that new location is (check this in the preferences).
If the photos are on the internal drive, you should probably move those and not the catalog, as the photos themselves take up a lot more space than the catalog.
To move the photos, see "Part 2 — Updating Folder Location" of this document: https://www.computer-darkroom.com/lr2_find_folder/find-folder.htm
If you choose the move the catalog file itself, then after the move and you confirm it is successful, go back and delete all files and subfolder in the folder that contained the catalog file on your internal hard disk.