Every website migration starts with the same promise - nothing will change except the design - and a distressing number end with the same phone call a month later: enquiries have dried up and nobody knows why. The traffic did not vanish mysteriously. It was lost in the move, one unglamorous detail at a time.
Where the rankings actually live
Google does not rank your website. It ranks pages - specific URLs with histories, titles, content and links pointing at them. Years of accumulated authority sit in those exact addresses. When a rebuild changes /our-services to /services without telling anyone, the old URL starts returning nothing, the links pointing at it hit a wall, and the authority it earned starts draining away. Multiply by every page that moved and you have a site that looks brand new and ranks like one too.
The same applies to the quieter furniture: page titles that were matching real searches, meta descriptions earning the click, the structured data that fed the map pack. Rebuilds that treat these as decoration lose them by accident.
Capture, port, verify
A migration that keeps its rankings is a discipline with an order. First CAPTURE: before anything changes, harvest the old site completely - every URL, every title and description, every redirect already in place, the sitemap, the robots rules. You cannot preserve what you never recorded.
Then PORT: carry those signals into the rebuild deliberately. Same URL structure where possible; an explicit 301 redirect for every address that must change; titles and descriptions carried or consciously improved; the sitemap and robots rules rebuilt to match.
Then VERIFY - the step almost everyone skips. Check every captured URL against the live site: does it resolve, does the redirect land where it should, does the title match what was promised? Not a sample. All of them, with a pass or fail against each.
You cannot preserve what you never recorded.
Trust measurement, not confidence
The uncomfortable lesson from every migration we have run: confidence is worthless, measurement is everything. A redirect that "should work" and returns the wrong status code loses authority silently. A page that "was carried over" with a different title drops for the search it used to win. The only migrations that keep their traffic are the ones where every claim was checked against the live site before and after the switch.
Nexus bakes this in as a three-stage migration tool - capture, port, verify, with a parity check per URL and the failures listed until they are fixed. However you do it, do it in that order. Moving house is no excuse for losing the post.