How to Migrate a Website Without Losing Organic Traffic

“We redesigned our site and traffic dropped 40%.”

We hear this more often than we should. It’s the most predictable disaster in SEO — and one of the most preventable.

The idea that migrations inevitably lose traffic is a myth perpetuated by agencies who don’t know how to manage them. Done properly, a migration can actually improve organic performance. You’re moving to a faster platform, cleaning up years of technical debt, and fixing architectural issues that were holding you back.

The question isn’t whether to migrate. It’s how to do it without leaving your rankings behind.

Why Migrations Lose Traffic (When They Do)

Traffic loss after a migration almost always comes down to one of four causes:

1. Broken or Missing Redirects

The #1 killer. Old URLs that don’t redirect to their new equivalents return 404 errors. Google can’t find your content, drops the old pages from the index, and has to discover and rank the new pages from scratch.

A single missing redirect on your highest-traffic page can account for a 10%+ traffic drop. Multiply that across dozens of missed redirects and the numbers get brutal.

2. Content Changes That Remove Ranking Signals

Redesigns love to “simplify” pages. That 1,200-word service page that ranks #2 for your most valuable keyword gets trimmed to 300 words because someone decided it “looked cleaner.”

Google ranked the old page because of its content depth, keyword coverage, and topical comprehensiveness. Remove that content and you remove the reasons Google ranked it.

3. Technical Regressions

The new platform is slower. The new design loads 3MB hero images. JavaScript rendering delays content visibility. Core Web Vitals scores tank.

Performance regressions directly impact rankings, especially on mobile where Google uses mobile-first indexing.

4. Crawling and Indexing Issues

New robots.txt rules accidentally block important sections. XML sitemaps reference old URLs. Canonical tags point to staging URLs. Noindex tags get left on pages from development.

These are usually quick fixes — but only if you catch them immediately. Left for weeks, they cause significant index coverage loss.

The Process That Preserves Traffic

Here’s the condensed version of what we do for every migration. Each step is non-negotiable.

Phase 1: Baseline Everything

Before touching anything, capture the current state:

Traffic baseline: Export 6 months of organic traffic data by landing page from GA4. You need per-page data, not just site totals. A site-level total can mask individual page losses behind other page gains.

Ranking baseline: Snapshot all keyword positions. Focus on the keywords driving actual traffic and revenue, not vanity terms.

Backlink baseline: Export every page that receives external links and how many referring domains each has.

Technical baseline: Core Web Vitals, index coverage, crawl stats, current redirects.

This baseline is your reference point for the next 90 days. Without it, you can’t measure impact.

Phase 2: Map Everything

The redirect map is the most important document in the migration. We build it page by page:

1-to-1 mapping: Every old URL gets mapped to a specific new URL. Not “all old blog posts redirect to /blog.” Each old post redirects to its specific new URL.

Content equivalence: The new page should serve the same search intent as the old page. Redirecting a product page to a category page is a signal mismatch — Google may treat it as a soft 404.

Chain cleanup: If old redirects already exist (A → B), and B is moving to C, map A → C directly. Chains waste crawl budget and dilute PageRank.

Priority tiers: Mark pages as P1 (high traffic + backlinks), P2 (some traffic or backlinks), P3 (low value). P1 pages get manual verification. P3 pages get automated checks.

Phase 3: Content Audit

For every page that currently ranks, we compare old content to new:

Title tags: Same primary keyword targeting? Same or better click-through rate appeal?
H1 and heading structure: Does the new page cover the same subtopics?
Body content: Word count isn’t everything, but if you’re cutting 1,000 words and replacing them with nothing, you need a good reason.
Internal links: Is the new page linked from the same (or more) internal pages?
Schema markup: Is structured data preserved?

Where the redesign team has removed or significantly changed content on a ranking page, we flag it and work with them to find a solution that satisfies both design goals and SEO requirements.

Phase 4: Staging Audit

Before launch, we crawl the staging site completely:

All redirects tested (every line in the map verified)
No broken internal links
Canonical tags pointing to correct new URLs (not staging domain)
Robots.txt allows appropriate crawling
XML sitemaps include all new canonical URLs
No noindex tags on pages that should be indexed
Core Web Vitals meet or exceed baseline
All tracking codes present and firing

If the staging audit reveals issues, launch gets delayed until they’re fixed. No exceptions. A delayed launch is better than a botched one.

Phase 5: Controlled Launch

We don’t launch and hope. We launch and verify:

Hour 1: Deploy and immediately run automated redirect verification across the full map. Fix any failures.

Hour 2-6: Monitor Search Console for crawl errors. Monitor server logs for 404 spikes. Submit new sitemaps.

Day 1-3: Request indexing of P1 pages. Monitor keyword positions for any immediate drops. Verify Google is discovering and crawling the new site structure.

Week 1: Daily traffic comparison vs baseline. Daily crawl error checks. Fix edge cases as they surface.

Phase 6: 90-Day Monitoring

The migration isn’t “done” until traffic has stabilised at or above pre-migration levels.

Week 2-4: Keyword position stabilisation. Most migrations see some fluctuation in the first 2-3 weeks as Google recrawls and reassesses. This is normal. Sustained drops beyond 3 weeks indicate an issue.

Month 2: Full traffic comparison by landing page. Identify any pages that dropped and diagnose the cause — usually a redirect issue, content change, or technical problem.

Month 3: Final comparison against baseline. If traffic is at or above pre-migration levels, the migration is complete. If specific pages are still underperforming, we investigate and remediate.

Migrations That Gain Traffic

It’s not unusual for well-executed migrations to improve organic traffic. Here’s why:

Faster platform: Moving from a bloated CMS to a performant framework (like Astro, Next.js, or a modern headless setup) improves Core Web Vitals. Better performance = better rankings.

Cleaner architecture: Migrations are an opportunity to fix years of accumulated technical debt — broken redirects, duplicate content, orphaned pages, cannibalising URLs.

Better content structure: Reorganising content into proper topical clusters with clear internal linking often improves rankings for the entire cluster.

Mobile improvement: If the old site had a mediocre mobile experience, a modern responsive redesign immediately benefits from mobile-first indexing.

The key is using the migration as an opportunity to fix problems, not just move them to new URLs.

Red Flags to Watch For

During any migration project, these are warning signs that things are heading toward trouble:

“We’ll handle SEO after launch” — this always ends badly
No dedicated SEO resource on the project — someone needs to own this
Redirect map built the week before launch — it should be built months before
“Can we just redirect everything to the homepage?” — no
Staging site has noindex/robots block and nobody’s tracking it — verify before launch
Content being cut for design reasons with no SEO review — flag immediately
Launch scheduled for Friday or before a holiday — push back

The Bottom Line

Website migrations are high-stakes technical projects. They’re not something you “figure out” during development or clean up after launch. The preparation that happens before a single redirect is written determines whether your traffic survives.

If you’re planning a migration — platform change, redesign, domain move — and want to protect your organic traffic, talk to us about SEO migration services. We’ve managed enough migrations to know where the bodies are buried.