BibLaTeX footcite shorten long URL

Question

Is it possible to automatically shorten long URLs in the footcite (e.g. to 20 chars) and add a "..." after that? Is it also possible to trim a URL after the TLD?

Here are two examples:

Footcite now:

Footcite should be (more or less):

Here is my MWE:

\documentclass{scrartcl}

\usepackage[backend=biber, sorting=nyt, maxcitenames=2, maxbibnames=2, firstinits=true, isbn=false, doi=false, url=false, style=authoryear, dashed=false]{biblatex}

\renewcommand*{\multinamedelim}{\slash\space} % Delimiter should be a "/"
\appto{\biburlsetup}{\renewcommand*{\UrlFont}{\normalfont}} % show URL w/o color

\begin{filecontents}{bib_data.bib}
    @online{gs1_aisbl_epc_2016,
    title = {{{EPC Information Services}} ({{EPCIS}}) {{Standard Release}} 1.2},
    url = {https://www.gs1.org/sites/default/files/docs/epc/EPCIS-Standard-1.2-r-2016-09-29.pdf},
    urldate = {2018-03-09},
    date = {2016-09},
    author = {{GS1 AISBL}},
}
\end{filecontents}

\addbibresource{bib_data.bib}

\DeclareCiteCommand{\footciteonline}[\mkbibfootnote] 
    {\usebibmacro{prenote}}
    {\usebibmacro{citeindex}
    \printnames{author}
    (\printfield{year})
    \newunit\newblock
    \printfield{title}
    \newunit\newblock
    \usebibmacro{url+urldate}
    \newunit\newblock
    \setunit{\labelnamepunct}
}
  {\addsemicolon\space}
  {\usebibmacro{postnote}}


\begin{document}
Lorem Ipsum.\footciteonline{gs1_aisbl_epc_2016}

\printbibliography
\end{document}

Thanks for your help.

Let me know if you need more information.

Answer 1

The following code uses Biber's sourcemapping to extract the TLD of URLs with 50 or more characters using RegExp. It then writes the TLD to the verba field. \footciteonline is then set up to print the shortened URL from verba if available and not the long URL from url.

\documentclass{scrartcl}
\usepackage[backend=biber, style=authoryear, dashed=false, maxcitenames=2, maxbibnames=2, giveninits=true, uniquename=init, isbn=false, doi=false, url=false]{biblatex}
\usepackage{hyperref}

\renewcommand*{\multinamedelim}{\slash\space} % Delimiter should be a "/"
\appto{\biburlsetup}{\renewcommand*{\UrlFont}{\normalfont}} % show URL w/o color

\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
    @online{gs1_aisbl_epc_2016,
    title = {{{EPC Information Services}} ({{EPCIS}}) {{Standard Release}} 1.2},
    url = {https://www.gs1.org/sites/default/files/docs/epc/EPCIS-Standard-1.2-r-2016-09-29.pdf},
    urldate = {2018-03-09},
    date = {2016-09},
    author = {{GS1 AISBL}},
}
@online{Bundesamt2016,
  address     = {Wiesbaden},
  author      = {{Statistisches Bundesamt}},
  institution = {Statistisches Bundesamt},
  title       = {Bildungsstand der Bevölkerung},
  date        = {2016-11},% date ist besser als year und month
  url         = {https://www.destatis.de/GPStatistik/receive/DEHeft_heft_00057188},
}
@online{elk:bronto,
  address     = {London},
  author      = {Anne Elk},
  institution = {University of Monthy},
  title       = {On the Theory of Brontosauruses},
  date        = {1972},
  url         = {http://www.example.edu/~elk/bronto.pdf},
}
\end{filecontents}

\addbibresource{\jobname.bib}

\DeclareCiteCommand{\footciteonline}[\mkbibfootnote] 
  {\usebibmacro{prenote}}
  {\usedriver
     {\renewbibmacro*{url}{\iffieldundef{verba}{\printfield{url}}{\printfield{verba}}}}
     {\thefield{entrytype}}}
  {\addsemicolon\space}
  {\usebibmacro{postnote}}

\DeclareSourcemap{
  \maps[datatype=bibtex]{
    \map{
      \step[fieldsource=url, match=\regexp{.{50,}}, final]
      \step[fieldset=verba, origfieldval]
      \step[fieldsource=verba, match=\regexp{\A(ht|f)tp(s)?:\/\/([^/]+).*}, replace=\regexp{$1tp$2://$3/...}]
    }
  }
}

\DeclareFieldFormat{verba}{%
  \mkbibacro{URL}\addcolon\space
  \ifhyperref
    {\href{\thefield{url}}{\nolinkurl{#1}}}
    {\nolinkurl{#1}}}

\begin{document}
Lorem\footciteonline{gs1_aisbl_epc_2016} Ipsum\footciteonline{Bundesamt2016} dolor\footciteonline{elk:bronto} sit amet.

\printbibliography
\end{document}