When a website migration goes badly, people blame the new design or the new platform. In my experience the cause is usually a spreadsheet nobody built: the list of every old URL and where it should go.
That list is the redirect map. It is boring, it takes a few hours, and it is the single most important thing between a clean launch and a month of watching traffic fall.
What it does
Every page on your old site has an address. Other sites link to it, Google has it indexed, and customers have it bookmarked. If the new site uses different addresses and nothing connects old to new, all of that value points at an error page.
A redirect map pairs each old address with its replacement, so the server can send visitors and search engines to the right place with a permanent (301) redirect.
Building one that holds up
Start with more than one source. A CMS export will miss things, so combine the old sitemap, your analytics landing pages, the pages Search Console shows, and a fresh crawl. Old PDFs and forgotten campaign pages show up here, and they are often the ones with outside links.
Then sort by importance. Some pages earn real traffic or backlinks and deserve careful matching. Others are junk from 2016. Giving them all the same attention wastes time.
Every URL gets one outcome: keep it, move it, merge it into another page, or retire it. Retiring is fine, but it should be a decision, not something that happens by accident.
When you match pages, send each one to its closest equivalent. Sending everything to the homepage is the lazy version, and search engines treat it as a weak signal. Also point each old URL directly at its final destination. A redirect that leads to another redirect slows things down and wastes crawl effort.
Finally, test the entire list, not a sample. Run it against staging, and run it again against the live domain on launch day.
The mistakes I see most
- Trailing slash and http/https variants nobody thought about, so the same page loads at three addresses.
- Old query-string URLs from marketing campaigns.
- A staging password or noindex tag that quietly survives into production.
- Internal links in the content still pointing at old URLs, so every click takes a detour.
- DNS changes that break email or form handling because nobody checked what depended on them.
After launch
Open Search Console and watch crawl errors and indexing for the first few weeks. Some movement is normal. A sharp drop on a page that used to matter usually points to a redirect or canonical problem you can actually find and fix.
Nobody can promise that rankings will hold through a migration, and I would be wary of anyone who does. What you can do is remove the avoidable risks, and this is the biggest one.
I wrote a longer checklist covering the rest of a redesign: the technical SEO checklist a redesign usually breaks. If you are moving between platforms, here is how we handle website migrations at CoderCorn.
I'm Abdul Haseeb Sadiq, founder of CoderCorn, a web design, development and managed hosting agency.
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