I just ran into a strange phenomenon: On Windows 10 I can have as many portable Chromium based browsers open at the same time as I wish, eg. Slimjet, Centbowser, Brave and Edge parallel side by side. Since my Windows 10 PC is in repair right now, I had to recur on my Windws 7 PC for a while. I use Centbrowser portable and found Supermium portable which was new to me, so I thought to give it a try. However, when I have Cent already running and want to open Supermium I get a "there is an instance of Supermium already runing.Please close all instances of Supermium before opening a new one" (It is not I counterchecked in Task Manager, the only Browser open is Cent Portable). Is this phenomenon peculiar to Supermium or Windows 7? The other way round - starting Supermium first and then Cent seems to work, at least it did yesterday.
 
      
 Visit the Community page
 Visit the Community page Join our forums
 Join our forums Subscribe to our email newsletter
 Subscribe to our email newsletter Subscribe with RSS
 Subscribe with RSS Follow us on BlueSky
 Follow us on BlueSky Follow us on Facebook
 Follow us on Facebook Follow us on LinkedIn
 Follow us on LinkedIn Follow us on Mastodon
 Follow us on Mastodon
The only one of those browsers we officially release and support is Supermium, the others you list we don't even have test releases, so they definitely weren't sourced from us and we can't really comment on how any of those other browsers are configured to run.
It is probable that your copy of Centbrowser is simply not checking for an existing running process like Supermium is, so opening Centbrowser after Supermium may screw up your settings in one, the other, or both.
It's based on the EXE. Supermium is chrome.exe. It's likely the others are, too. You shouldn't run more than one Chrome-based browser and expect them not to step on each other a bit whether local or portable.
Sometimes, the impossible can become possible, if you're awesome!