clickable links in plainTeX document

Is it possible to define clickable links in a plainTeX document when compiled with pdftex? As far as I can see there is no support in plainTeX for this feature.

For creating clickable links in pdf documents generated from a TeX (plainTex) document you can use this code:

\newif\ifpdfmode
\ifx\pdfoutput\undefined
\else
    \ifnum\pdfoutput>0 \pdfmodetrue\fi
\fi

\def\url#1{%
    % turn off the special meaning of ~ inside \url{}.
    \begingroup\catcode`\~=12\catcode`\_=12\relax
    \ifpdfmode
        \pdfstartlink user{
            /Subtype /Link
            % w/o this you get an ugly box around the URL.
            /Border [ 0 0 0 ]   % radius, radius, line thickness
            /A <<
                /Type /Action
                /S /URI
                /URI (https://#1)
        >>
        }%
        {\tt#1}%
        \pdfendlink{}%
    \else
        %{\tt https\negthinspace:\negthinspace/\negthinspace/#1}%
        {\tt#1}%
    \fi
    \endgroup}

that you can save in a file named lib/url.sty. Note that it injects some pdf code because links are not natively supported by TeX (even when using the pdftex compiler).

Once done it's just a question of using the macro url in your TeX code:

\input lib/url.sty

My preferred site is \url{stackoverflow.com}!

The macro \url works also when the document is not compiled with pdftex. In this case the conditional ifpdfmode will be set to false by the compiler and a simple text formatted with the \tt font will be rendered instead.

You can find a "live" example here: https://github.com/madrisan/cv