Most website migration plans end at go-live. That is where the real work begins.
The first 30 days after a migration are when search engines decide what to do with your new site. Google needs to recrawl every URL, reindex the content, and reassign the ranking signals that your old site accumulated over years. If something is broken during that window, you will not find out from your developer. You will find out from your traffic report, weeks later, when the damage is already done.
A well-executed migration will still cause a temporary traffic dip. That is normal. The question is whether the dip recovers or becomes permanent. The answer depends entirely on what you do in the first 30 days.
What happens to your traffic immediately after launch?
Even a perfectly planned migration will cause a short-term dip in organic traffic. Expect a 5-10% drop in the first week or two. This is not a sign that something went wrong. It is a sign that Google is processing the changes.
Here is what is happening behind the scenes. Googlebot visits your old URLs, encounters the 301 redirects you set up, and follows them to the new URLs. It then needs to crawl the new pages, evaluate the content, and update the index. That takes time.
For medium-sized websites (a few hundred pages), most pages will move in the index within a few weeks. For larger sites with thousands of pages, complete re-indexing can take 3 to 6 months (SEMrush Migration Checklist). This is why Google recommends that you retain control of your old site domain for at least 180 days after a migration. The redirects need to stay active for the entire re-indexing period.
The temporary dip should stabilize within two to three weeks. If it does not, something needs attention.
What should you monitor in week one?
Week one is about catching technical problems before they compound. Here is the short list.
Google Search Console indexing report. The Page indexing report in Search Console shows you new pages being indexed and old pages being deindexed in near real-time. You want to see the new URL count climbing while the old URL count drops. If neither is moving, Google has not started processing the migration yet.
Redirect validation. Spot-check your highest-value URLs manually. Open the old URL in a browser and confirm it lands on the correct new page. Pay special attention to pages that drive the most organic traffic and pages with the most backlinks. Automated checks are better, but manual verification catches things that scripts miss.
404 errors. Check the Pages report in Search Console for new 404 errors. A small number is normal. A sudden spike means your redirect map has gaps. Fix these immediately. Every day a high-value URL returns a 404 is a day that Google is devaluing the equity behind it.
Analytics continuity. Verify that your tracking is firing correctly on every page of the new site. Migrations are notorious for breaking analytics setups. If your tracking snippet was hardcoded in the old template and the new site uses a different tag manager configuration, you could have pages with zero tracking. A drop in reported traffic is not always a real traffic drop. Sometimes it is a measurement gap.
Crawl stats. In Search Console under Settings, the Crawl Stats report shows how aggressively Google is crawling the new site. A spike in crawl activity after launch is a good sign. It means Google has noticed the changes and is actively re-indexing.
What should you monitor in weeks two through four?
Once the immediate technical fires are handled, shift focus to performance trends.
Organic traffic vs. pre-migration benchmarks. Compare weekly traffic to the same period before the migration. Account for seasonality. A dip in week one is expected. A continued decline in week three needs investigation.
Ranking changes for priority keywords. Track your top 20 to 50 keywords daily. Some fluctuation is normal as Google reassigns signals. But if a keyword that ranked in position 3 drops to position 30 and stays there, the corresponding page likely has a problem. Check whether the redirect is working, whether the new page has the same content depth, and whether the internal linking structure still supports that page.
Conversion tracking. Forms, CTAs, checkout flows. These need verification after every migration, not just the pages themselves. We have seen migrations where every page loaded perfectly but the contact form submissions went to a dead endpoint because the backend URL changed. This is part of what the Essential Launch Framework is designed to catch.
Core Web Vitals in the field. Lab data (Lighthouse, PageSpeed Insights) gives you a preview. Field data from the Chrome User Experience Report tells you what real users experience. It takes about 28 days for field data to accumulate after a migration. By week four, you should have enough data to spot performance regressions. If your Largest Contentful Paint went from 1.8 seconds to 3.5 seconds, that will eventually affect rankings.
User behavior metrics. Bounce rate, session duration, pages per session. These are not direct ranking factors, but they tell you whether the new site is working for real visitors. A spike in bounce rate on a specific page often means the redirect is landing users on the wrong content.
What are the warning signs that something went wrong?
Some problems are obvious. Others are subtle and only show up in the data weeks later. Here is what to watch for.
A sudden 404 spike. If Search Console shows hundreds of new 404 errors in the first week, your redirect map is incomplete. This is the most common post-migration issue and the most urgent to fix.
Pages stuck in “Discovered, currently not indexed.” This status in Search Console means Google knows the page exists but has not chosen to index it. A few pages in this state is normal. Dozens of important pages stuck here suggests a crawlability issue. Check your robots.txt, your sitemap, and your internal linking.
Organic traffic still declining after week three. The initial dip should flatten and begin recovering by the end of week two. If traffic is still falling in week three, something structural is wrong. Common causes include redirect chains that slow down crawling, missing content that Google previously valued, or a noindex tag that accidentally made it into production.
Redirect chains creating slow loads. A redirect from A to B to C adds latency with every hop. If your migration introduced new redirects on top of existing ones from a previous migration, you could have three- or four-hop chains that add hundreds of milliseconds to every request. Flatten them.
Old URLs still appearing in search results. If Google is still showing your old URLs in search results after three weeks, the redirects may not be working as expected. Verify the HTTP response codes. A 302 (temporary) redirect tells Google to keep the old URL in the index. You need 301s (permanent) for a migration.
Why do most agencies skip this phase?
Because the project is “done.” The contract said design, build, launch. Post-launch monitoring was never in scope. The agency has already moved on to the next project.
This is not malicious. It is structural. Traditional project-based billing creates a natural incentive to finish and move on. The agency delivered what was promised. The fact that the hard part comes after launch is not their problem.
But it is your problem. A migration that loses 30% of organic traffic has a real cost. For a business that generates leads through search, that is lost revenue every single day until the traffic recovers. If the issues are not caught quickly, some of that traffic never comes back.
This is why Essential Code stays involved after launch. Our website subscription model is designed specifically for this. We do not hand off a site and disappear. We monitor the post-launch data, catch issues early, and fix them before they become permanent. The migration is not done when the site goes live. It is done when the traffic has recovered and the new site is outperforming the old one.
If you are planning a migration or just finished one and want someone watching the data, the website subscription is the natural next step. It is ongoing accountability, not just a one-time delivery.