Website Migration SEO Checklist: Move With 301 and Don’t Lose Authority

Changing domains, restructuring directories, moving from HTTP to HTTPS — the scariest part is never a bug on launch night; it’s opening the report two weeks later and finding organic traffic down sixty percent. What a website migration actually moves isn’t files, it’s the signals search engines spent years building up: backlinks, indexation, click history.

Migration without losing authority comes down to three things — a one-to-one 301 mapping table covering every old URL, keeping the old domain’s redirect ability alive for at least 12 months, and high-frequency monitoring for 30 days after launch. Sending hundreds of old pages to the homepage in bulk, redirect chains longer than one hop, and forgetting to sync the sitemap are the three most common traffic-killers. Run the checklist and authority transfer usually completes within 2 to 8 weeks; short-term fluctuation of 10% to 20% is normal.

1. Export the migration baseline: crawl the whole site and export URLs with status codes, a traffic ranking from the last 12 months, backlink report, and current indexation count — don’t delete any of it for three months after the move.
2. Build a one-to-one 301 mapping table: each old URL points to the content-closest new URL, one hop, done; if no matching page exists, point to a same-topic category page rather than dumping everything on the homepage.
3. Switch in order on launch day: set DNS TTL to 300 seconds 24 hours ahead, let crawlers through before the switch and confirm no leftover robots.txt blocking, and spot-check response headers after redirects take effect ahead of DNS.
4. Sync the sitemap and submit the change: submit the new sitemap right away and keep a copy of the old-URL sitemap; in the domain-change case, file an address-change request in the webmaster console.
5. Monitor heavily for 30 days after launch: export the 404 list daily and patch mappings, compare new vs. old indexation weekly, and watch whether crawls transfer and core keywords recover around week three.

Take stock of the house before migrating

Before touching anything, do a full asset snapshot. Without a baseline, after launch you can’t tell whether it’s rankings, indexation, or a changed metric definition that dropped. Export at least four sets of data and don’t delete them for three months after the move.

• Crawl the whole site with a crawler tool and export every accessible URL with its status code, including parameter pages, pagination, and attachment pages.
• Pull a 12-month landing-page traffic ranking from your analytics, mark the head pages that contribute the top 80% of traffic — those pages’ redirects can’t afford a mistake.
• Export the backlink report and put URLs that have inbound links on their own list. The addresses people point at you are the main channels for authority transfer.
• Record current indexation, core-keyword positions, and average CTR as the comparison baseline after launch.
• Back up the old site’s robots.txt, sitemap.xml, and canonical config, and check against the robots.txt and sitemap guide for any leftover historical blocking rules.

How to build a 301 mapping table that doesn’t lose authority

There’s only one mapping principle: old URL points to the content-closest new URL, one-to-one, one hop. Bulk-301-ing hundreds of old pages to the homepage is telling the crawler this content collectively vanished — Google treats such redirects as soft 404s and authority basically never comes back. When no matching page exists, prefer a same-topic category or archive page over the homepage.

Flatten the redirect chains too. A two-hop structure where A jumps to B and B jumps to C wastes signal strength and adds an extra DNS and TLS handshake, slowing time to first byte. Before launch, run the mapping table on a test environment and confirm every old URL is a single 301 straight to its destination. Historical leftover redirects should be cleaned up as well — the debugging flow is in the dead links and redirect chain cleanup article.

Launch day, in this order

Launch-day actions have a strict order. Get the order wrong and crawlers can grab a batch of 404s before the redirect rules take effect, leaving errors in the index report for half a month. Pick a low-traffic weekday window with the whole team online.

• Set the new site’s DNS TTL to 300 seconds 24 hours ahead so you can flip back fast.
• Let crawlers through on the new site before the switch and confirm no leftover Disallow: / in robots.txt — that’s the #1 rookie mistake in redesign incidents.
• Redirect rules take effect before DNS; right after the switch, spot-check the response headers of 30 head URLs with a command line, confirming status 301 and Location arriving in one hop.
• Submit the new sitemap.xml immediately, and keep an old-URL sitemap submitted to the search engine to help crawlers discover the redirects faster.
• File an address-change request in the search engine’s webmaster console — this noticeably speeds up signal transfer in the domain-change case.
• Re-verify analytics code, conversion goals, and event tracking on the new site so data gaps aren’t misread as traffic drops.

The 30-day monitoring rhythm after launch

Migration success or failure shows between week two and week six. First three days watch errors, first two weeks watch indexation, after a month look at rankings. Make the Search Console coverage report a daily check, focusing on the trend curves of “crawled but not indexed” and “not found (404)”.

• Export the 404 list daily, add URLs with traffic or backlinks to the mapping table, and fix them the same day.
• Compare new vs. old indexation weekly. The new site should catch up to 90%+ of the old site’s indexation within four weeks.
• Watch the crawler distribution in server logs — is it still repeatedly hitting old URLs? When the crawl center of gravity shifts, it usually means the redirects are fully recognized.
• Track core-keyword rankings weekly. For pages that haven’t recovered by week three, check one by one whether the redirect target’s content similarity is high enough.

These traps flip you over the easiest

Most common isn’t technical difficulty, it’s missing process items. Redirect rules covered only the main site but forgot the blog subdirectory; after the new site goes live, canonical still points at the old domain, effectively returning the authority — the debugging approach for that kind of conflict is in the canonical and duplicate content handling article. Static resources like images and PDFs often get their old addresses skipped, yet they often carry substantial backlinks. Pagination parameter pages change form under the new architecture and need their own set of redirect rules.

Before landing, put these four things on the calendar: today, export the old site’s full URL list, traffic ranking, and backlink pages and archive all three as the migration baseline; this week, finish the one-to-one mapping table and manually re-check the redirect targets of the top 100 URLs one by one; before launch, run a full redirect check on the test environment to confirm zero chains and zero loops; after launch, record indexation and 404 counts for 30 straight days as a one-page migration health sheet. With these four scheduled, the migration fight stops being scary.

FAQ

What does a site migration fear losing most?

Organic traffic. The three most common causes: old URLs without one-to-one 301s, hundreds of pages bulk-redirected to the homepage and treated as soft 404s, and the old domain’s redirect ability not kept for 12 months.

How do I build the 301 mapping table?

Old URL points to the content-closest new URL, one-to-one, one hop. When no matching page exists, prefer a same-topic category or archive page over the homepage.

How long should I keep the old domain?

Keep the redirect ability for at least 12 months, renew if you can. If it expires and gets squatted, the redirect chain breaks and years of backlink authority are all cut off — the risk far outweighs the renewal fee.

How long before authority recovers after migration?

Authority transfer usually completes within 2 to 8 weeks; short-term traffic fluctuation of 10% to 20% is normal. First three days watch errors, first two weeks watch indexation, after a month look at rankings.

What do I do first on launch day?

Set DNS TTL to 300 seconds 24 hours ahead; before the switch confirm no Disallow: / in robots.txt; let redirect rules take effect before DNS and spot-check 30 head URLs afterward.