SEO Site Migration Checklist

Why migrations go wrong

Most SEO ranking drops after a migration come from a small set of predictable problems: redirect chains created by stacking new redirects on top of old ones, pages that became non-indexable due to overly broad noindex rules or incorrect canonicals, and URLs that were simply missed from the redirect map and now return 404.

The right time to catch all of these is immediately after migration - not when Google has already dropped rankings weeks later. Crawly gives you the data to do that.

Step 1: Pre-migration crawl

Before anything changes, run a full crawl of the existing site. This is your baseline. It captures every URL that currently exists, every title, every H1, every status code, and every indexability status.

Export the list of all indexable pages. This becomes your redirect checklist - every indexable URL on the current site should either exist at the same URL on the new site, or have a 301 redirect pointing to its equivalent.

Pay particular attention to pages that:

• Have inbound links (check your backlink tool)
• Are in your XML sitemap
• Appear in Google Search Console with impressions or clicks

Step 2: Verify redirects with List Mode

After the migration goes live, take the list of old URLs from your pre-migration crawl and paste them into Crawly's List Mode. Run a crawl. Crawly will fetch each URL and record what it returns.

What you are checking:

• Every URL should return either a 200 (if the URL stayed the same) or a 301 redirect to the new URL
• No URL should return a 404 - that means the redirect was missed
• No URL should return a 302 - migrations should use permanent 301 redirects
• No redirect should chain through multiple hops - go directly from old URL to new URL

For individual URL spot-checks, use the Redirect Checker to see the full redirect chain for any URL.

Step 3: Post-migration full crawl

Run a full spider crawl of the new site. This discovers the new URL structure, finds any pages that exist on the new platform but were not in your redirect map, and captures all on-page data for the migrated site.

Step 4: Compare pre and post crawls

Use Crawl Comparison to diff the pre-migration crawl against the post-migration crawl. If you are new to this feature, the crawl comparison guide explains how to read the three lists in detail. Review each list:

Removed URLs

Any URL from the baseline that is missing from the new crawl either got redirected (expected) or was missed entirely (problem). Cross-reference removed URLs against your redirect map. Any URL that is removed but has no redirect in place needs one.

Added URLs

New URLs created by the new platform. Common examples: new tag pages, author archive pages, pagination variants, or URLs with tracking parameters. Verify these are intentional and properly canonicalised if they are duplicates.

Changed URLs - indexability

This is the most important thing to check. Any URL that was indexable in the baseline but is now non-indexable in the new crawl is a potential ranking loss. Common causes:

• A noindex tag in the new template that was not in the old one
• A canonical pointing to the wrong URL (e.g. all pages canonicalising to the homepage)
• A robots.txt rule on the new site that is too broad and blocks real content

Changed URLs - titles and H1s

Title changes after a migration are common and often unintentional. A new template might output titles in a different format, append the site name differently, or not pull the custom title from the CMS correctly. Review changed titles and confirm the new versions are correct.

Step 5: Check for redirect chains

Migrations are a common source of redirect chains. If the old site already had redirects in place (e.g. from a previous migration), and the new migration added more redirects on top, you now have chains.

In Crawly's Issues tab, look for Redirect chains. Any chain found in the post-migration crawl needs to be collapsed to a single direct 301.