Fails to parse <a href="http://io/" rel="nofollow">http://io/</a> as valid URL. Same with IDNs, <a href="http://пример.испытание/" rel="nofollow">http://пример.испытание/</a>. Okay, that's obscure cases, but when you're writing yet another link shortener you really should know quite a bit about URIs (and IRIs).<p>Practical problem is, service does not make distinction between http and https schemes - typing in <a href="https://example.org/" rel="nofollow">https://example.org/</a> yields <a href="http://www.donotlink.com/ZG" rel="nofollow">http://www.donotlink.com/ZG</a> which leads to <a href="http://example.org/" rel="nofollow">http://example.org/</a>.