StumbleUpon has been around since the early 2000s. In the early days it was a fun site to just be taken to a random site. Until June 30, 2018, you can still do this. If you go there now, they will encourage you to Join Mix. Mix is a related service. You can join Mix with your Facebook or Google account or with an email address.
You can use StumbleUpon.com before it goes away this week. But you’ll have to remember your old login. Assuming you may have joined at one time and no longer use it.
How it worked is, you would go to StumbleUpon.com and join, then slick on a button to find a random cool webpage. The company that owns Mix.com, Expa, wants to take Mix.com to the next level and combine social and semantic personalization to the user experience. They want to make it easy to organize your content into collections. They will be transitioning StumbleUpon accounts over to Mix.
Some other companies under the Expa umbrella are Uber (driver service), Haus (helps you sell your own house and keep more of the money than through a broker), Prefer (a way to grow your business through referrals), Ando (food delivery service), Spot (a way to find things to do based on referals), Operator (a way to find what you are looking for). These are a few of Expa companies.