miji.beShort URLs are convenient tools, but their ease of use occasionally triggers unexpected trouble. Looking back, short URL incidents range from laughable ones to ones that grew into international problems. These cases point to precautions for using short URLs.
First, the problem of randomly generated short URLs accidentally forming inappropriate words. Some services auto-generate random alphanumeric slugs. With 6-character random strings, there are theoretically about 56.8 billion combinations, and some of them may match vulgar or discriminatory words. A slug can end up overlapping with a word that has a vulgar meaning in English. To prevent this, some services use "banned word lists" (blacklists) to keep inappropriate strings from being generated, but catching inappropriate words language by language is difficult.
The 2010 "Libya domain incident" highlighted geopolitical risks. Some short URL services used Libya's country-code top-level domain `.ly` (bit.ly, ow.ly, and others). In 2010, Libya's domain authority seized `vb.ly` for linking to content violating Islamic law, showing that services depending on a specific country's TLD can be suddenly shut down by that country's legal or political decisions. Bit.ly also held `j.mp` as an alternative domain.
There are also cases where short URLs published by public agencies became unusable through configuration errors or specification changes. If the redirect destination of a short URL placed in an official document is set incorrectly, readers are sent to an unrelated page. Once a document has been distributed, fixes may not keep up. In Japan, if a short URL service changes its specifications after a municipality prints a disaster information short URL, the information may become inaccessible during a disaster.
Large-scale link loss from service shutdowns is also part of short URL history. In 2009, the short URL service tr.im announced a temporary suspension, raising concerns that a large number of links would stop working at once. The announcement was later withdrawn, but the episode showed a weakness: when a short URL service disappears, the links made there can no longer be used; Google's goo.gl also ended its console and API in 2019, which shows that even a major short URL service has no guarantee of permanence. A lesson from these cases is to consider whether a link will still work in 10 years and to use the organization's own domain for important links.