biblatex has a number of counters which when set to non-zero positive values less than 10000 allow breaks in urls in the bibliography. The specific counters are
biburlnumpenalty
biburlucpenalty
biburllcpenalty
for breaks after numbers, uppercase letters and lowercase letters, respectively. In your case it suffices to set the lowercase penalty to 9000; lower values encourage breaks more (or rather discourage them less). The setting is done value via \setcounter:
\documentclass[12pt,english,a4paper]{article}%
\usepackage[backend=bibtex,defernumbers=true,sorting=nty]{biblatex}%
\usepackage[breaklinks,plainpages=false]{hyperref}%
\def\UrlBreaks{\do\/\do\a\do\b\do\c\do\d\do\e\do\f\do\g\do\h\do\i\do\j\do\k\do\l\do\m\do\n\do\o\do\p\do\q\do\r\do\s\do\t\do\u\do\v\do\w\do\x\do\y\do\z\do\A\do\B\do\C\do\D\do\E\do\F\do\G\do\H\do\I\do\J\do\K\do\L\do\M\do\N\do\O\do\P\do\Q\do\R\do\S\do\T\do\U\do\V\do\W\do\X\do\Y\do\Z\do0\do1\do2\do3\do4\do5\do6\do7\do8\do9\do=\do/\do.\do:}
\setcounter{biburllcpenalty}{9000}
\addbibresource{Biblio.bib}
\begin{document}
See \cite{citation} for further details or visit \url{http://www.joifewoirjecpwoirjcpewrijcpenwrjcpnewrjicpnwerjincpejricpejripcne.com}.
\printbibliography
\end{document}
When choosing values for these penalties it is useful to note that biblatex's defaults are
\UrlBigBreakPenalty 100
for breaks after : and -, and
\UrlBreakPenalty 200
for breaks after most punctuation characters. You want to set the other penalties significantly higher, so that breaks after numbers and letters are of a lower prioriy than those after punctuation marks. If you need to change the two \Url...BreakPenaltys above then it is via the unusual syntax of
\mathchardef\UrlBreakPenalty=200\relax
Traditional typographical practice is to avoid hyphenating such words, so such a rule was coded by Knuth into the TeX program.
However, it is still possible to insert a hyphen that allows breaks, by fooling TeX into thinking we have two separate words (by inserting empty glue). This can be quite easily done if we're willing to type a special sequence like \Hyphdash or \-/ instead of a hyphen, which is what is provided by packages like extdash. But if we insist on typing regular hyphens into the TeX file, then “classical” TeX engines (meaning, other than LuaTeX) provide only one way of having regular hyphens be treated as something else, and that is to change the catcode of - to active, so that it becomes a macro that expands to something longer. But this would cause problems whenever - is used anywhere other than regular text, which is quite common (see examples of the problem in Steven's answer). I imagine that if a good solution existed for this in the classical TeX world, some package like extdash would have covered it.
(Actually, there's a perfectly sensible approach which for some reason is not very popular in the TeX world: and that is to preprocess your input file with some “smart” external script, replacing only the hyphens that occur in regular text with \Hyphdash (or its expansion) or whatever. But for some reason, people want to do everything inside TeX.)
With LuaTeX, which allows greater access to TeX internals, a lot of things become possible, and a lot of catcode and macro-related headaches are gone. For example, LuaTeX has a hyphenate callback which can be used to modify the regular hyphenation it does. This callback gets a list of nodes, into which we can insert discretionary nodes (hyphens) wherever we choose. This is much easier than having to do everything with macros (it is hard to set up appropriate input which later expands into exactly what we need, with no other interference). And there's even a lang.hyphenate function, which we can use to simply do what the regular hyphenation does.
The following seems to work: put the following in a file, say hyphenateall.lua:
function hyphenate_always(head, tail)
local n = head
while n do
if node.type(n.id) == 'glyph' and n.char == string.byte('-') then
-- Insert an infinite penalty before, and a zero-width glue node after, the hyphen.
-- Like writing "\nobreak-\hspace{0pt}" or equivalently "\penalty10000-\hskip0pt"
local p = node.new(node.id('penalty'))
p.penalty = 10000
head, p = node.insert_before(head, n, p)
local g = node.new(node.id('glue'))
head, g = node.insert_after(head, n, g)
n = g
end
n = n.next
end
lang.hyphenate(head, tail)
end
luatexbase.add_to_callback('hyphenate', hyphenate_always, 'Hyphenate even words containing hyphens')
and just put \directlua{require('hyphenateall')} in your .tex file.
For example (borrowing the example from Steven's answer):
\documentclass{article}
% Not needed -- used in this example just to show it's not needed :-)
\newcommand\?{\nobreak-\hspace{0pt}}
\begin{document}
\begin{minipage}[t]{0in}
\hbox{Before:} often hungry Works: often\?hungry What about: often-hungry
\end{minipage}\hspace{1in}%
\directlua{require('hyphenateall')}%
\begin{minipage}[t]{0in}
\hbox{After:} often hungry Works: often\?hungry What about: often-hungry
\end{minipage}
\end{document}
Note that after the \directlua call, we did not need the special syntax to get the extra hyphenation.
Best Answer
You can exploit
xurl.