Printed URLs are inconvenient and i just noticed, that there is a LaTeX package to generate QRCodes.
I think using QRcodes to aid with URLs could turn out quite nice, so i used the code below to generate a QRcode in the margin everywhere a \url is used:
\usepackage{hyperref}
\usepackage{qrcode}
\let\oldUrl\url
\renewcommand*{\url}[1]{\oldUrl{#1}\marginpar{\qrcode[nolink]{#1}}}
First of all: The result of this kind of blew my mind, because it very easily did, what i wanted to achieve.
There is one drawback i would like to solve: Because of the high density of URLs in the Bibliography not all QRcodes do appear next to the related entry.
So I would like to extend the height of a bibliography entry with an URL field, so that it matches the height of the QRcode in the margin.
This is kindof related to "Info boxes in bibliography", but there the info boxes also did not create extra space for the bibliography entry. So i want something similiar to "Vertical space depending on height of marginpar", but in the bibliography.
I'm using biblatex for my bibliography.
The MWE:
\documentclass[]{article}
\begin{filecontents}{\jobname.bib}
@misc{example1,
title = {Example.com},
url = {http://example.com}
}
@misc{example2,
title = {Example.com},
url = {http://example.com}
}
@misc{example3,
title = {Example.com},
url = {http://example.com}
}
@misc{example4,
title = {Example.com},
url = {http://example.com}
}
@misc{example5,
title = {Example.com},
url = {http://example.com}
}
\end{filecontents}
\usepackage[backend=biber,sorting=nyt,style=ieee]{biblatex}
\addbibresource{\jobname}
\usepackage{qrcode}
\let\oldUrl\url
\renewcommand*{\url}[1]{\oldUrl{#1}\marginpar{\qrcode[nolink]{#1}}}
\begin{document}
\nocite{*}
~ % Type something....
\printbibliography
\end{document}


AtEveryBibitem(or something like that), but as you can see from your screenshot, that attempt produces irregular spacing for entrys without an URL field. also it will add the space even when the bibliography entry was long enough to cover the full height of the qrcode, so it will only work, when the bibliography entry has only 1 line. – MaPePeR Aug 01 '16 at 18:34\marginnotewithAtEveryBibitemallows to align the qrcode at the top of the entry, but i have not yet found a way to specify a minimum height for the entry. (If there is a qrcode the entry should be at least as high as the height of the qrcode) – MaPePeR Aug 02 '16 at 12:37