Website Migration SEO Checklist: What to Monitor Before and After

A website migration SEO checklist covers three moments: what you record before the move, what you verify on launch day, and what you watch for the month after. Traffic is rarely lost because the plan was wrong. It is lost because a noindex or a robots.txt rule survives the switch and nobody notices for a fortnight. Deltio snapshots the sitemap daily, checks title, meta description, H1, canonical and hreflang on every URL, and tests uptime every 10 minutes, so a regression arrives as an alert instead of a traffic drop. From £20 a month on the annual Starter plan, with a 14-day free trial.

Migration is the one job where an agency can lose a client's traffic in an afternoon. Domain change, replatform, HTTP to HTTPS, a redesign that keeps the same URLs: the failure mode is always the same. Something from the staging configuration goes live and the site quietly stops being crawlable. This checklist is built around that risk, not around a generic project plan.

Before the move: record the site as it is today

You cannot prove a migration went well without a baseline. Take it at least a week before launch, not the night before.

• The full URL list. Export the current sitemap and keep the file. It becomes the list you check the new site against. Our guide to XML sitemap best practices covers what a healthy one looks like.
• On-page state. Title, meta description, H1, canonical and hreflang for every URL that earns traffic. This is your before picture, and it is the only way to spot a template-level rewrite later.
• The tag stack. Which analytics and marketing tags are installed, and their IDs: GA4, Google Tag Manager, Meta Pixel, whatever the client uses.
• Uptime and response time. A normal week of data, so you know what slow looks like once the new stack is live.

Pre-launch: the four things that break migrations

Run these on staging, then run them again on production within minutes of the switch. Not the next morning.

• robots.txt. Staging is almost always disallowed. If that file ships, the site drops out of the crawl. Here is how to check robots.txt line by line.
• noindex. Same problem, page level. A noindex tag left in a shared template will take out every page that uses it.
• Canonicals. Absolute, one per page, pointing at the new URLs. Canonicals still aimed at the old domain are common and expensive.
• hreflang. On a multilingual site, every language version has to reference the new URLs, and the references have to be reciprocal.

Launch day: the first two hours

• Redirects. Every URL in your baseline should resolve in one hop to its real equivalent. Chains and blanket redirects to the homepage waste the equity you are trying to move.
• SSL. New domain, new certificate. Confirm it is valid, covers both www and the apex, and is not due to expire in three weeks.
• Status codes and availability. Cutover is when servers fall over and firewalls start blocking anything that looks like a bot, crawlers included.
• Tags. Analytics goes missing in migrations more often than rankings do. Check GA4 and GTM fire on the new templates, with the same IDs as before.

The first 30 days

The expensive damage is the damage nobody looks for after week one.

• URLs quietly dropping out of the sitemap as the CMS settles.
• Titles and meta descriptions rewritten by the new template on a whole section.
• A canonical change shipped with a routine deploy.
• Response time drifting once traffic is back at full volume.

How Deltio covers a migration

Add the site before the migration and Deltio holds the before picture for you. It snapshots the sitemap every day and shows URLs added, removed or changed, so a section that stops being listed is visible the next morning, with the last seven snapshots kept for comparison. The SEO scanner checks title, meta description, H1, canonical, lang and hreflang on every URL and compares consecutive scans, which is how a template-level regression gets caught rather than reported by the client. A robots.txt change triggers an immediate alert with a diff of the added and removed lines. Uptime is checked every 10 minutes, with a notification when the site goes down and another when it returns. SSL is watched with warnings 30 days and 1 day before expiry, and domain expiry is tracked over RDAP. Marketing tags are checked on every URL, so a missing GA4 or a changed GTM ID becomes an alert instead of a discovery in October. Everything lands in email or Slack.

Set it up before the next one

The checklist only works if the before picture exists, and you cannot create it retroactively. Add the client site now, let it run for a week, and walk into the migration with data instead of a memory. The 14-day free trial covers a launch weekend comfortably.