After tweaking the settings it's great for viewing raw Jenkins logs.

Remember to set the proper permissions, then it works like a charm with almost any ansi and ascii art. Many thanks.

Simple, to the point, does exactly what it says. Thanks, Ben! :)

I hope this will be extended with supporting for ascii art in 2ch. It just requires font "MS DOS Gothic" and size "16px(12pt)" and space between the lines is "2px".
I just don't wanna change font settings in firefox because it affects whole part of browser, so I have been looking for extension, and I am here. Unfortunately this RetroText does not supprt ascii art for 2ch...

EDIT:Thanks for help!