Make a detailed list of site-specific checks. Generic migration checklists are a good starting point, but they need to be customized for the website and CMS.
Manually test localized pages across different templates to ensure correct hreflang and canonical tag implementation.
Dig deeper: How to run a successful site migration from start to finish
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JavaScript rendering failures
JavaScript-driven content that users can see but search bots can’t is a common and often overlooked issue.
This typically happens when widgets or content sections rely on JavaScript to render, but the scripts aren’t fully crawlable or properly executed by search engine bots.
(Google offers a great resource to help you understand JavaScript basics.)
If you’re unsure how a widget works, use this simple test:
Does it display the full content immediately, or does it require user interaction?
If it’s the latter, it likely relies on JavaScript, meaning search and AI bots might not see everything.
To catch this issue, run both a JavaScript-enabled crawl and a pure HTML crawl, then compare the results.
A quick manual test can also help.
Search for a specific sentence or element from the widget in your rendered HTML source.
If it’s missing, search bots are probably missing it too.
Resolving this often requires improving server-side rendering or ensuring that scripts load properly for both users and crawlers.
Since website migrations often leave little time for testing, make it a priority to run these two crawls post-migration to identify and fix any rendering issues.
Dig deeper: A guide to diagnosing common JavaScript SEO issues
Loss of tracking data
Tracking data loss can be a subtle yet costly post-migration issue.
In one real-world case, everything initially appeared fine. Analytics data was flowing and visits were being logged.
However, after a few days, it became clear that users arriving via paid ads were losing their tracking parameters as they navigated the site.
This meant subsequent pageviews within the same session were no longer attributed to the original paid campaign, disrupting remarketing efforts.
The cause?
Improper handling of URL parameters during the migration.
Website migrations require cross-team monitoring, not just from the SEO team.
While this issue didn’t directly impact SEO rankings, it still had major consequences.
Before migration begins, triple-check your plan to ensure all relevant teams are involved.
Migration testing should go beyond SEO, incorporating analytics, development, and marketing teams to safeguard tracking parameters and user attribution.
Each team should have pre-migration reports for comparison after launch.
While planning may not fall under SEO’s direct responsibility, identifying gaps in the project plan and raising concerns is essential.
Dig deeper: 12 SEO pitfalls to avoid during a website platform migration
Disappeared pages
This case is a perfect example of why having pre-migration data is crucial.
Everything appeared flawless during testing.
The site functioned as expected on staging and even in production with internal DNS switched.
But as soon as external DNS was activated, a third of the blog posts disappeared.
The rest of the site remained intact, making the issue easy to overlook.
With all teams focused on testing tracking, forms, redirects, hreflang tags, and canonicals, no one initially noticed the missing pages.
Ironically, it wasn’t an SEO tool or a developer check that caught the problem, but a regional manager.
A few days before migration, she updated a blog image and wanted to verify that the change had transferred.
Not only was the image missing, but the entire blog post was gone.
I’ll admit, I can’t explain exactly what caused this from a technical perspective.
But the takeaway is clear: always conduct a full audit before migration begins.
Using a crawler’s comparison mode can quickly highlight discrepancies like this before they become major problems.
Impact on admin settings
Not every issue affects SEO, but that doesn’t mean it won’t cause problems.
During a backend update, we encountered an unexpected challenge: Lumar and Screaming Frog were overwhelming the CMS admin panel.
Each time a crawl was initiated, the surge in requests made it nearly impossible for editors to update content or make changes.
It’s important to remember that you’re not the only one using these tools.
Crawlers are frequently employed for competitor analysis, meaning your website and CMS must function properly even under heavy crawling pressure.
In some organizations, SEO teams don’t have direct access to the CMS or manage content updates.
If that’s the case, ensure content teams go through their usual workflows with test pieces after migration.
Coordinating this with SEO crawls helps assess how resilient your system truly is.
The biggest mistake: Underestimating post-migration monitoring
Website migrations, revamps, redesigns, updates. Whatever you call them, they’re always complex.
One of the biggest mistakes you can make is underestimating the challenges involved.
Any change carries the risk of something going wrong.
Some errors, like broken redirects or missing pages, are immediately noticeable.
Others, such as tracking failures or JavaScript rendering issues, may take time to detect.
That’s why post-migration monitoring is just as critical as the migration itself.
The best way to mitigate these risks is to:
Create a detailed project plan covering all potential issues.
Document everything.
Run audits before and after migration.
Collaborate across teams.
A successful migration isn’t just about making the switch; it’s an ongoing process of monitoring, testing, and improving.
Dig deeper: How to speed up site migrations with AI-powered redirect mapping
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