13 Great Firefox Extensions for Web Professionals Like most web developers or SEO professionals, I use a vast array of tools to get the job done. I use a combination of desktop and web applications, some purchased and some free. Everyone I know has downloaded a free copy of Mozilla Firefox, but few realize that by installing some of the 1,500 free extensions they can eliminate the need for most of the other applications they currently use. Below are my 13 favorite extensions for web professionals (in no particular order): with arraydevelopersjobprofessionalsseotoolsvastwebby 5 users