@happynuclear - Thank you for such quick responses.
Like I said before, I have a list with a few hundred thousand users from an old system. I split the list up into smaller lists, with 50,000 lines per list. The list is already scrubbed and I put the list in the column order your plugin recommends.
In the admin panel, I go to Users > Add Multiple Users > CSV/TXT Upload
My CSV file is in the order: username, password, email, role, firstname, lastname, website
When I try to upload the .TXT file, I get an error:
Error: Not a valid file type! Only .csv and .txt files may be uploaded.
When I convert the file to a comma delimited .CSV file, I do not get this error. I get taken to a page that says:
The following user information has been extracted from your uploaded file.
Please review your extracted CSV data in the text field below and, if necessary, customize the column order appropriate to your CSV data structure (see Custom Column Order information below).
...and my data is listed in the scroll-able box.
However, when I click the button "Create User Information" I get taken to a page that says:
Please review the user information below to correct any errors or to add additional information for each user and click the Add All Users button to process your new user accounts.
...and only one line is listed, and it is blank. There is two buttons that say "Add All Users" and "Add Extra Row" but none of my data has been populated.
I've tried reducing the file to 25,000 lines and have the same issue.
I continued testing by reducing the file to 10,000 lines, I get a table of populated data on the following screen, but it never finishes loading before the browser crashes (tried on both Firefox and Chrome).
A 10,000 line .CSV file is only 905.8Kb so I'm not sure why it causes such problems. To me, importing anything less than 10,000 lines at a time, is useless.
More testing effort was put in by reducing the file to 5,000 lines, and still, it never finishes loading before the browser crashes (tried on both Firefox and Chrome).
A 5,000 line .CSV file is only 452.7Kb yet still there are problems.
I finally got a different result, when I reduced the file again, to 2,500 lines, which is only 225.9Kb, the browser (both of them) stopped crashing, but both were extremely slow and sluggish. It would take hours to get to the bottom of a 2500 line list, via scrolling.
When I click the "Add All Users" button, I get a screen that says "New User User Accounts Processed" at the top and "New User Account Registration Details:" at the bottom, but none of the user accounts were added.
Only with a list of 1000 lines, do the browsers operate efficiently (or as expected). Yet, still, when I click the "Add All Users" button, I get a screen that says "New User User Accounts Processed" at the top and "New User Account Registration Details:" at the bottom, but none of the user accounts were added. (FYI: There is something wrong with the bottom "Add All Users" button, only the top one seems to work correctly).
With list which is just under 1000 lines, it acts like it is working and goes through all the process of working, but never actually adds the users.
I don't know what is going on, but I've tried this on two separate, clean installs of WordPress, and I'm getting the same/similar results. It just isn't working correctly with lists of 1000 lines or larger, and isn't worth the effort for lists less than 10,000 lines.