<p>From your description it looks like you're only willing to affect external links, so:
</p>
<dl><dd><dl><dt> If you want this to affect your account only:
</dt></dl></dd></dl><p>You could add to your
/global.js something like this (or your
/common.js if you want this to only be applied in specific wiki(s)):
</p>
<div dir="ltr" class="mw-geshi mw-content-ltr"><div class="javascript source-javascript">
<span class="coMULTI">/* make all external links open in a new tab */</span>
$<span class="br0">(</span><span class="st0">"body"</span><span class="br0">)</span>.<span class="me1">click</span><span class="br0">(</span><span class="kw1">function</span><span class="br0">(</span>e<span class="br0">)</span> <span class="br0">{</span>
<span class="kw1">var</span> a <span class="sy0">=</span> e.<span class="me1">target</span><span class="sy0">;</span>
<span class="kw1">if</span> <span class="br0">(</span>a.<span class="me1">nodeName</span>.<span class="me1">toLowerCase</span><span class="br0">(</span><span class="br0">)</span> <span class="sy0">==</span> <span class="st0">"a"</span> <span class="sy0">&&</span> a.<span class="me1">href</span>.<span class="me1">indexOf</span><span class="br0">(</span>location.<span class="me1">origin</span> <span class="sy0">+</span> <span class="st0">"/"</span><span class="br0">)</span> <span class="sy0">!=</span> <span class="nu0">0</span><span class="br0">)</span> <span class="br0">{</span>
<span class="co1">// user clicked an external link</span>
$<span class="br0">(</span>a<span class="br0">)</span>.<span class="me1">attr</span><span class="br0">(</span><span class="st0">"target"</span><span class="sy0">,</span> <span class="st0">"_blank"</span><span class="br0">)</span><span class="sy0">;</span>
<span class="br0">}</span>
<span class="br0">}</span><span class="br0">)</span><span class="sy0">;</span></div></div>
<dl><dd><dl><dt> If you want this to affect everyone in an entire wiki :
</dt></dl></dd></dl><p>I'm not sure if the use of JavaScript for this behavior matches the
customization policy, as i haven't made any public wiki scripts in a few years. If you are an admin there, you could
ask a Wikia staff member to enable
such behavior.
</p><p>However, note that if a reader wants to open a link in a new tab, they could do just that whether they are in pc or mobile. Maybe it's just my opinion, but sites don't let me open a link the way i want really grind my gears.
</p>