Site Migration Link Protection Checklist
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A before, launch day, and after checklist that keeps a site migration, redesign, or domain change from turning into a wave of broken links.

[ ] Before: crawl the current site completely and export every URL with its status code, title, and inbound internal link count.
[ ] Before: pull the list of URLs that received traffic in the last 12 months from analytics and add any that the crawl missed.
[ ] Before: export the URLs that have backlinks from other sites and flag them as must-redirect entries.
[ ] Before: include non-HTML assets in the inventory: PDFs, images, downloads, feeds, and any file linked from emails or print materials.
[ ] Before: build a redirect map that pairs every old URL with one new destination, one to one wherever possible, and store it in version control.
[ ] Before: review the map entries for the home page, navigation, top traffic pages, and key landing pages by hand rather than trusting pattern rules.
[ ] Before: choose a fallback for old URLs with no equivalent: a real 404 or 410 page, never a blanket redirect to the home page.
[ ] Before: stage the new site, crawl it, and confirm that every page in the redirect map resolves to a 200 status on the staging environment.
[ ] Before: test the redirect rules against the full old URL list and check that no chain runs longer than one hop and no loop exists.
[ ] Before: confirm that the new 404 page keeps site navigation, offers search, and returns a true 404 status rather than a 200.
[ ] Before: name one owner for redirects, one for content links, and one for monitoring during the launch window, and agree on a rollback trigger.
[ ] Launch day: keep the old environment reachable so a rollback is possible for at least the first days after the switch.
[ ] Launch day: run the redirect test again against production as soon as DNS or the new deploy is live.
[ ] Launch day: watch the server error rate and 404 count in real time and compare them with the baseline from the week before.
[ ] Launch day: crawl the new production site and check internal links in navigation, footer, and templates first.
[ ] Launch day: update the sitemap, submit it to search engine webmaster tools, and verify that robots rules are not blocking the new URLs.
[ ] After: crawl the new site again within the first week and compare the results against the pre-migration URL export.
[ ] After: review webmaster tool crawl error reports for old URLs that were never added to the redirect map and add them.
[ ] After: check redirect rules written under pressure for chains, wildcard patterns that send unrelated pages to one destination, and gaps.
[ ] After: update internal links so they point directly at the new URLs instead of relying on the redirect for every click.
[ ] After: contact the sites behind your most valuable backlinks and ask them to update the link if the old URL cannot be redirected.
[ ] After: keep the redirects in place for years rather than weeks and record the date and reason for each rule so future cleanups have context.
[ ] After: schedule a recurring crawl or continuous monitoring so leftover breaks surface within days rather than when a customer reports them.