How to find a Steam Group ID

To find your Steam group ID, first get the URL of your Steam group. It will look similar to:

https://steamcommunity.com/groups/nameofgroup

Then add the following to the end of the URL:

/memberslistxml/?xml=1

That gives you a URL similar to:

https://steamcommunity.com/groups/nameofgroup/memberslistxml/?xml=1

The page will show XML code. Near the top, look for <groupID64>. For example:

<memberList>
  <groupID64>103249292485930254</groupID64>
</memberList>

Copy the number from inside the <groupID64> tags. That number is your Steam Group ID.

You can use that ID on your Space Engineers server when enabling Steam group whitelist.

Old Method

Make sure you are a member of the Steam group and signed into your Steam account. On the group page, click Invite Friends. The group ID may appear as a long number at the end of the URL bar. In the Steam app, enable the setting that displays the Steam URL bar first.