Reference
What is Site migration?
A site migration is changing domain, host, platform or URL structure, or several at once. It survives or fails on one thing: a complete old-URL to new-URL redirect map, deployed as single-hop 301 redirects before anything else changes. Everything else in a migration is recoverable; a missing redirect map is not.
Also called: domain change · replatforming
What to capture before you touch anything
- A crawl of every URL currently returning 200 — this list is the migration
- Search Console performance data for the last 16 months
- Current rankings for your top terms, so "did it work" has an answer
- The backlink profile, because those pages matter most
- Current indexed page count, which is the earliest warning signal afterwards
The rules for the redirect map
- Every old URL maps to the closest equivalent new URL, never en masse to the home page
- One hop only — chains bleed signal
- 301, not 302, unless the move genuinely is temporary
- Keep them for at least a year; removing them at six months undoes the work
The special case worth knowing
Migrating off a free subdomain with no rankings, traffic or links is trivial — there is nothing to preserve. Move immediately, because the cost only rises as more cards, CVs and profiles carry the old address.
Where this is covered in depth
A definition can only go so far. Migrating a site without losing what it took years to earn covers this properly — 3 minutes, free, no email required.
Who wrote this
Anas Bin Masud builds e-commerce sites and does technical SEO for businesses in the UK, Canada and Pakistan. These definitions come from client work rather than from a content brief — where an entry describes a mistake, it is usually one found on a real site. More about how I work.