Zero-downtime website migration checklist

Take a full backup (files + DB) and stage the site on the new host via temporary URL / hosts. Verify admin, forms, checkout and cron before touching DNS. Lower A/AAAA TTL to ~300s a day ahead. After cutover, sync a final DB delta and keep the old server for 48–72 hours. Share cases: WordPress, stores, mail on the same domain — where migrations fail most often.