Further to Caramdir's (User 3872) 2011 question; I have a similar MWE as in that question, hence:

\documentclass{book}
\usepackage{hyperref}
\usepackage{url}
\begin{document}
text\footnote{\eur50}
\end{document}


This works for me with other url's in footnote. This example, however, seems too long and breaks by the % sign (shown here in grey).

Q:How can one load the long url with the % sign included as it is in the url? (so without \ in front).

• Hello, LION! :-) Oct 21 '14 at 12:02
• Have you tried \@? Oct 21 '14 at 12:12
• \eur50 is an illegal name for the URL. I get several errors with the example, so the output is incorrect. Use \eurl or anything else provided it's letters only. Oct 21 '14 at 12:13
• Could you please show which question do you refer to? I wasn't able to find it.
– yo'
Oct 21 '14 at 12:24
• With egreg's suggested change your code works fine for me. Oct 21 '14 at 12:34

Only letters are allowed in the commands defined with \urldef, so \eur50 is illegal and, indeed, several errors appear when processing your example.

The problem is described in this TeX FAQ; basically \newcommand{\eur50}{...} is not legal.

You could use digits by using a different strategy:

\documentclass{book}
\usepackage{hyperref}

\newcommand{\namedurldef}[1]{%
\expandafter\urldef\csname#1\endcsname
}
\newcommand{\namedurl}[1]{\csname#1\endcsname}