I posted some of this info on another post a few months ago, but doubt that many saw it, so I thought I would put it out there in a separate post. It comes in handy when you are trying to verify information by someone who has posted, and are wondering if they are a first time poster or someone who has posted here before.
Every member here with an account is assigned a user number. Right now poster user numbers are in the 930,000s. If you are curious about another poster (or curious about your own user number), you can find it pretty quickly.
On a Macbook, hover your cursor over the poster's name, and a URL will appear in small text in the lower left hand corner. At the end of the URL is the poster's user ID number. For example, mine is https://community.ricksteves.com/users/30997. My user number is 30997, so I've been here for a good long while.
On an iPhone, long-press the user's name and a pop-up will appear with the user number.
On an Android phone, long press on the user's name and then tap again at the top of the popup (on the partial link that you'll see displayed to the right of the photo of Rick Steves). Or turn your phone sideways first, and then long press on the user's name. The entire link will be displayed, including the user number at the end of the link.
Special thanks to CWSocial for the Android instructions