This may not be a Firefox / Ubuntu specific issue. When I Copy / Paste a web link with _ and ( ) it is rendered as %20, %28, and %29. Yet in the Firefox URL these % symbols do not appear. The %20 is particularly weird because the _ itself does render in the URL: https://www.capitalsecuritybank.com/en/PDF/CSB_%20Account_%20Application_%20Form_%20%28Personal%29.pdf Can anyone explain why the URL is different when Copied / Pasted?