How do I download my Yahoo Group's Members list?

If your group has 1000 or fewer members:

To obtain a list of your Yahoo Group members you can go to the Manage Members page and in the Actions menu Export (download) a CSV or TSV format file. It is best to open the file in a spreadsheet like Excel, then you can easily copy the Email column to paste into the Direct Add or Invite page. Note: this is only for groups with 1000 or fewer members, due to Yahoo's Export restriction.

If your group has more than 1000 members:

Use PG Offline ($25 USD) or the chrome application for downloading members (free). PGO produces a CSV format file, the file produced by the Chrome app is tab-delimited. As of December 16, both of these options still work, but you must be a Moderator of the Y!G to get the email addresses. 

While described as a "Chrome" application, it runs in at least one other web browser similarly based on Chromium, Vivaldi. Therefore it should work in Chromium, Opera, Chrome and others.

The application can be found at http://yahoogroupedia.pbworks.com/w/page/79909487/Chrome Application to Download Members

Once loaded, in Vivaldi place vivaldi://apps in the address bar/field to reveal the page with its button.

Follow directions. The app generates a .txt file, which is actually tab-delimited (TSV).

Start your spreadsheet program, open/import it as tab-delimited file. Save in the spreadsheet format you desire.

Copy the column with the addresses to use in the Group.io Invitation or Direct Add process, and paste them into the box.

Downloading Yahoo Group's Member List

Another method of downloading the entire Yahoo Group's member list has been documented by the Health-Related YahooGroup Archives website. 

This method requires Excel and Notepad as well as Google Chrome or Brave browsers, but not with FireFox.

You need to by a Moderator or Owner of the Yahoo Group to use this method.

Go to Management / Manage Members

Starting at "First Name", select the entire list until you get to the bottom (this can take some time,

When you have marked the entire list this way, right click and copy the selected entries and past it into an empty Notepad window.

In Notepad, File / Save As / Save as type: All Files (*.*) / groupmembers.prn

It is important to save the text file with the .prn extension, not .txt

Using Microsoft Excel, open the groupmembers.prn file and the Text Import Wizard opens on Step 1

Set Delimited, tick My data has headers and change File origin to: 650001 : Unicode (UTF-8) and click on Next

In Step 2, ensure Tab is ticked and click on Next

In Step 3, click on each column and define the Column data format as Text (incl. date column)

Click on Finish and the data is inserted into a new document

Name Column B "Full name" and use Find and Replace to remove the "Profile picture " text with Replace All

Select and delete the empty column A

Label I1 "Groups" and J2 "Full address"

Select the entire worksheet and use Data / Sort

Tick My data has headers and Sort by Delivery / OK

On the lines with "Daily Digest", type "digest" in column I respectively

On the lines with "Individual Emails", leave column I empty

On the lines with "No Email", type "nomail" in column I respectively

On the lines with "Special Notices", type "nomail" in column I respectively

In J2, enter the formula; =IF(ISBLANK(A2);IF(ISBLANK(D2);E2;D2&" <"&E2&">");A2&" <"&E2&">")&" "&I2

Copy from J2 into the following rows that contain entries.

Check the formatting in column J, if it looks strange, delete the respective empty A and D fields 

You now have the correctly formatted addresses for using in Direct Add for your new groups.io group in column J.

A video demonstrating the above procedure can be seen here.