Digital Preservation & Link Rot
The average webpage doesn't survive very long — a meaningful fraction of links go dead within a few years. The Internet Archive's Wayback Machine crawls and stores snapshots of pages over time specifically to fight this, and anyone can manually save a page's current state to it. If a page matters enough to cite or rely on, it's worth archiving before it isn't there anymore.
How bad, specifically
A 2024 Pew Research Center study tracking a broad sample of webpages found that 38% of pages that existed in 2013 were no longer accessible a decade later, and roughly a quarter of all pages that existed at any point between 2013 and 2023 had gone dead by the end of that window.[1] The same study found 54% of Wikipedia pages contain at least one dead reference link, 23% of news pages do, and roughly half of the URLs cited in US Supreme Court opinions no longer resolve to their original content. A separate, independently run study of nine years of published links found more than 66% dead by the end of that period.[2] None of these numbers agree exactly, but they all land in the same range: link rot isn't a rare edge case, it's closer to the default outcome for a link nobody actively maintains.
Two different failure modes
"Link rot" usually gets used for two genuinely different problems. Reference rot is the simple case — the URL returns a 404, the domain expired, the site shut down entirely. Content drift is quieter and arguably worse: the URL still works, but the page behind it has been edited, replaced, or repurposed since it was cited, so a link that looks fine is silently pointing at something other than what the citing author actually referenced. A snapshot service defends against both; a live URL defends against neither.
The tools, beyond the Wayback Machine
The Internet Archive's Wayback Machine is the largest and longest-running general-purpose web archive, but it's not the only option.[3] archive.today (also seen as archive.ph/archive.is under various mirror domains) takes a single, permanent, on-demand snapshot the moment you submit a URL — useful specifically because it can't be affected by a site's robots.txt asking crawlers to stay away, which the Wayback Machine has historically respected. Perma.cc, built and run by a consortium of law libraries, exists specifically to solve the Supreme Court citation problem above: it gives academic and legal citations a permanent link that won't rot.[4]
The practical habit
Archiving a page takes seconds and costs nothing; recovering a page that's genuinely gone (not indexed anywhere, never archived) is often simply impossible. The asymmetry is the whole argument for doing it before you need it, not after. The same asymmetry, on an institutional scale, is the entire story behind every burned library and every archive lost to a single fire or flood: a record that only ever existed in one place, gone the moment that one place is.