The four ways it happens
Your site ranks. That is why you are afraid to touch it. The fear is reasonable. The thing you are afraid of has four causes. All four are decided in the first week, before a single screen is designed.
- The redirect map is built from the sitemap. The sitemap is a file your old CMS wrote. It is often incomplete.
- Somebody tidies the slugs. An untidy URL that ranks is worth more than a clean one that does not.
- The redirects chain. Old URL to interim URL to new URL, often through a trailing-slash rule and an http-to-https rule on the way. Each hop is another place for a rule to be dropped during a hosting change.
- The query string gets dropped. A redirect that discards everything after the question mark strips the click ID off every paid visit that lands on an old URL. The ads keep spending. The conversions arrive unattributed.
Why the sitemap is the wrong source
On my last build the server served 19 URLs and the sitemap listed 12. I found the other seven by asking the origin server directly, one URL at a time, before DNS moved. All 19 redirect in one hop.
So the map is assembled from five sources: the origin probe, your Search Console URL export, your analytics landing pages, a full crawl of the old site and its internal link graph. Every URL in that list is tested against staging as one set before launch. On that job, 19 of 19 legacy URLs redirect in a single hop to a live page. Verified by direct HTTP request against the live site on 9 September 2026.
The slug orthotics-australia was kept exactly as it was on that build. It already ranked.
Take the baseline before launch
When a redesign costs traffic, the usual story is that traffic fell after launch and there was no baseline to check against. I take a 90-day organic baseline from your own Search Console while the old site is still up. Ninety days after launch I run the same report against it.
A traffic graph nine days after launch means nothing. Give it the ninety days.
What I will and will not promise
Every URL your old site serves will redirect in a single hop to a live page on launch day. That means every URL your server answers, which is usually more than the sitemap lists.
If a legacy URL 404s in the first ninety days, or a page has lost its title, its H1, its canonical or its schema against the baseline snapshot, I fix it free.
I will not guarantee your traffic. Nobody controls Google's index. I will guarantee that nothing broke on my side, and I will give you the crawl that proves it. No vendor can promise traffic.
If someone else is building it
You do not have to change builder. A migration on its own is quoted after I have seen how many old pages need redirecting. Fixed quote after scope, before any deposit. It covers the origin probe, the redirect map, the baseline, and the full legacy set verified against the new site before DNS moves. It must be commissioned before launch, because the baseline cannot be taken after the old site is gone. Your builder keeps building. I own the URLs.
If your quote does not mention redirects, ask for the redirect map. If the answer is that it will be handled, ask to see the map before you pay a deposit.