Executives: migrating a website without losing your traffic
Google writes that permanent redirects do not cause a loss of PageRank, the measure of importance Google assigns to each page. What loses traffic during a migration is therefore not the redirect: it is the incomplete URL mapping table, and the omissions you discover three months later.
- Google states that 301 redirects, the rules that automatically send an old address to the new one, and other permanent redirects do not cause a loss of PageRank. The opposite belief makes businesses give up on necessary migrations.
- Rankings can fluctuate while Google recrawls and reindexes, that is, revisits every address and updates its results. Count a few weeks for a medium-sized site, longer for a large one.
- Googlebot, the robot Google uses to crawl sites, can follow up to ten hops in a redirect chain, but Google recommends redirecting directly to the final destination.
- The systematic omissions are embedded files, images, videos and scripts, which Google explicitly asks you to include in the migration plan.
- A migration is done section by section when the site is large. Google names it as an option, and it is what reduces the risk.
On this page
What is a URL mapping table
A URL mapping table is the exhaustive list matching every address on the old site to its address on the new one. It covers pages, but also downloadable files and embedded content. It is the one migration deliverable whose quality actually determines the outcome: a complete table makes the migration a non-event, a partial table produces a traffic loss proportional to what is missing.
What Google really says about the 301
This piece is written for executives and managers commissioning a redesign or a platform change. It covers the execution of the migration, not the decision to rebuild the site, which is covered elsewhere in our corpus.
The most persistent belief in this field holds that a redirect loses part of a page's value. It is false, and it costs real money: management teams postpone necessary migrations and keep paying for years for a platform that eats the budget and slows down sales.
Google writes that 301 redirects and other permanent redirects do not cause a loss of PageRank. The wording is direct, with no caveat or condition.
What does move, on the other hand, is time. Google states that with any significant change, rankings can fluctuate while it recrawls and reindexes the site. Count a few weeks for most pages of a medium-sized site, and longer for a large one.
This settling period is normal, and it is regularly mistaken for a failure. A management team that sees traffic drop three weeks after a migration often concludes the project failed and demands rushed fixes. Decide in advance how long you will observe before drawing a conclusion, and write it down.
The URL mapping table
It is the one deliverable that decides the outcome, and the one that quotes underestimate the most.
It matches every address on the old site to its address on the new one. Not just the important pages: every address, including the ones nobody visits anymore but that still receive links from outside.
Three sources combine to produce it. A full crawl of the old site, which gives you what exists. The list of addresses known to search engines, which gives you what they have indexed. And the list of pages that received traffic or links over the past twenty-four months, which gives you what actually matters.
The third source is the one that gets forgotten. A page that no longer appears in the navigation but still receives links from a media outlet or a professional association has a value its current traffic does not show, and replacing it would cost years of effort.
When a page disappears with no equivalent, the temptation is to redirect it to the homepage. That is bad practice: redirect to the closest page by topic, or accept the removal. Google warns that a page redirected in bulk to the homepage might be treated as a soft 404, a signal of irrelevance.
Redirect chains
This is the most common technical defect on sites that have already migrated once.
Google states that Googlebot can follow up to ten hops in a redirect chain. It still recommends redirecting the user directly to the final destination, and otherwise using a limited number of hops, ideally no more than three, at worst fewer than five.
The reason is twofold: chains increase response time for visitors, and not all browsers and agents accept long chains.
In practice, the businesses that inherit the problem are the ones migrating for the second or third time. If your old site was already redirecting older addresses, the new migration creates chains. Rework the historical rules and point every old address directly to the final destination, rather than stacking one more rule on top.
Google also recommends using server-side permanent redirects when technically possible, of the 301 or 308 type.
What gets forgotten every time
Embedded content. Google explicitly asks you to include the addresses of video, image, JavaScript and CSS files in the migration plan. These addresses must be moved like the rest of the site.
Downloadable documents. Spec sheets, warranties, manuals, forms. They often receive external links and end up returning errors without anyone noticing.
Tracking addresses. The ones used in your ads, your newsletters and your printed QR codes. A poster produced last year still points to the old address.
Advertising landing pages. They often live outside the main navigation and do not show up in a standard crawl.
Versions with and without a trailing slash. A tiny detail that produces duplicates or errors at scale.
The first two points explain most of the revenue losses discovered after the fact. The third explains the calls from clients who can no longer find a page they saw in a flyer, and every one of those calls is a sale that almost did not happen.
The real timeline
Google gives two useful indications to frame expectations.
The first is duration: a few weeks for most pages of a medium-sized site, longer for a large one. The delay depends largely on the number of addresses and the speed of your server.
The second is an option few businesses use: migrating the site section by section. On a large catalog, this approach considerably reduces the risk, because a problem detected in one section does not affect the others.
Google also mentions that submitting a sitemap, the file that lists all of a site's addresses for search engines, can help speed up the discovery of the new addresses.
One common-sense rule completes the picture: never migrate during your high season. The settling period is normal, and going through it in the weeks that carry the most sales turns a technical inconvenience into a direct margin loss. The cost of the same project can double depending on the month you choose.
What a failed migration costs
The calculation is done beforehand, to size the budget for the URL mapping table.
Take your annual organic revenue, that is, the sales attributable to unpaid search results. On a site generating $230,000 through that channel, a migration where 15% of the traffic never comes back represents $34,500 per year, and that loss repeats every year until it is corrected.
Compare that amount with the cost of a complete URL mapping table. On a site of a few thousand addresses, the work represents a few dozen hours. The trade-off is never close.
This cost goes unnoticed because it never shows up as a loss. Traffic is simply lower than before, and six months later nobody remembers exactly what the previous level was. Record your numbers before the migration and keep them.
After the switch, track four indicators every week for three months.
Page-not-found errors, which reveal the table's omissions. Every error that receives traffic gets fixed immediately, because it represents clients who arrive nowhere.
The number of indexed addresses, which should climb progressively back to its previous level. A prolonged stall signals a crawling problem rather than a normal delay.
Organic traffic by section, never as a total. A general drop is hard to interpret, a drop concentrated in one section points straight to the cause.
And the client inquiries received, which are the only measure that decides. Falling traffic with stable inquiries costs your revenue nothing. Stable traffic with falling inquiries is an urgent commercial problem, and the two situations are handled differently.
If the migration also changes your URL structure, that decision comes first, as we explain in our article on URL architecture.
What to require before approving a migration
These five points get settled at the quote stage. After launch, they become emergency fixes.
- Does the URL mapping table cover every address, including documents and embedded content?
- Have the historical redirects been reworked to avoid chains?
- Are your traffic, inquiry and organic revenue numbers recorded and stored before the switch?
- Is the migration done all at once or section by section, and why?
- How long will you observe before concluding there is a problem, and who decides on fixes?
A good answer presents a URL mapping table quantified in number of addresses. A weak answer talks about setting up the necessary redirects. A vendor whose plan does not include downloadable documents and embedded content will deliver a migration whose losses show up three months later.
Verifying a URL mapping table and recording your numbers before the switch is part of what we cover in a paid audit.
What is never delegated: recording your numbers before the switch, choosing the timing of the migration, and setting the observation period before drawing conclusions. What can be delegated: crawling the old site, building the URL mapping table, reworking the historical redirects, the implementation and the weekly monitoring. A business that records its traffic and inquiries the day before the switch can prove the migration worked. A business that did not will spend months debating the size of a revenue loss nobody can quantify, and the correction budget will be decided without any data.
The overall view of website design is in designing for three readers.
Starting from a blank page and want the migration planned from the design stage? See our work in web design.
Frequently asked questions about site migration
Does a redirect lose value?
No. Google writes that 301 redirects and other permanent redirects do not cause a loss of PageRank. What varies temporarily is rankings while Google recrawls and reindexes. This settling period is normal, carries no lasting cost, and is regularly mistaken for a failed migration.
How long before traffic comes back?
Google states that a few weeks are usually needed to move most pages of a medium-sized site in its index, and that the process takes longer for large sites. The speed depends largely on the number of addresses and the performance of your server. Set your observation period in advance.
Can removed pages be redirected to the homepage?
It is bad practice. Redirect to the closest page by topic, or accept the removal. A page redirected in bulk to the homepage might be treated as a soft 404, a signal of irrelevance, and you lose the benefit the redirect was supposed to bring.
What about the redirects already in place?
Rework them. If your old site was already redirecting older addresses, stacking a new rule creates a chain. Google recommends redirecting directly to the final destination, and otherwise staying under three hops. Point every historical address directly to its current destination.
Should you migrate all at once or by section?
Google explicitly mentions the option of migrating a site section by section. On a large catalog, this approach clearly reduces the risk: a problem detected in one section does not affect the others. On a site of a few dozen pages, migrating all at once is simpler and sufficient.
Which files get forgotten most often?
Embedded content, which Google explicitly asks you to include in the plan: video, image, JavaScript and CSS files. Then come downloadable documents, which receive external links, and the addresses used in your ads, newsletters and printed material. These three categories explain most of the losses discovered after the fact.
- Google Search Central, Site moves with URL changes, official documentation, accessed July 2026. Source for the absence of PageRank loss, the reindexing delays, the ten-hop limit, the recommendation on chains, the inclusion of embedded content and the section-by-section migration.
- Google, Search Console Help, Change of Address tool, accessed July 2026. Source for the recommendations on redirecting canonical pages and on grouping several migrations.
- Falia working framework, arithmetic of organic revenue loss. The amounts are explicit worked examples, to be redone with your actual organic revenue.
Gabriel almost always takes your first call and carries out your audit. He builds the strategy starting from your growth goal: where to put your budget, which market to test and how to connect each lead to a real sale in your CRM. He mainly leads engagements for three goals: Optimize the profitability of your digital campaigns, Develop a new market, and Generate demand and growth. With Geneviève, he also works on organic search (SEO), AI visibility (GEO) and conversion rate optimization (CRO). The sales a Google Ads or Meta Ads campaign brings in depend on the page that receives the click. He writes mainly about marketing strategy, paid advertising and measurement.
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