Auto detect already open browser instead of opening default one

I have multiple browsers on my system (Firefox, Google Chrome, and Chromium). I normally use one of them at a time based on my needs, but when other applications want to open a browser they always open their/system default browser. Is there an application or script that is able to detect if a browser is already running and use it as current default browser? **EDIT** I don't want a browser to detect its own instance! I want a browser requester program/script to detect any already open browser. - For example assume I have Firefox, Google Chrome and Chromium, and I click a link in a PDF file, and Chromium is already open. I want the link to be opened in Chromium. - At another time, Firefox is open. Then I want the link to be opened in Firefox. Actually, I want already open browser have more priority than the system default one.