I tried to do this when I blogged with MovableType and it’s a fool’s errand. You end up needing to cache all of the links somewhere and revalidate them periodi

I tried to do this when I blogged with MovableType and it’s a fool’s errand. You end up needing to cache all of the links somewhere and revalidate them periodically. But it's not enough to check for a 200 or 304 because the site could do a redesign and move the content around, the domain could expire, an RTBF demand could be served, etc. So you need to validate the content in some way to ensure you're still linking to what you more or less intended to in the past. So, yeah, then you end up linking to the archive.org page (and if it's not there you could submit it to archive.org for archiving). For a time archive.org delisted pages if the current robots.txt blocked access (even if the page was archived a decade ago), I can't verify if this is still the case. A really poorly quick scan of ~400 links from my decaying blog shows about 40% either do not resolve at all or return content from a link farm (another 30-40% appear to redirect to https versions of the site, but I didn't check further to see if the content was what was intended).