How did Google perceive our SEO migration to

A website migration is always a risky task. Just as a reminder, we changed our brand name in France from covoiturage to BlaBlaCar in April 2013. We decided to switch the domain name only beginning June 2015 because we thought it was time to do it in France: blablacar is now much more popular than the term covoiturage. The main goal was to unify our brand domain names everywhere, the SEO challenge was to make sure traffic loss would be kept to a minimum.

What we did?

  • Set up 301 redirects for all pages from to (e.g. to, and update all internal links.
  • Warn Google that the domain has moved in Google Webmaster Tools.
  • Update external links on most important websites. The 1st thing was to update the links on social platforms & on partner websites. Of course, you can’t update everything and this can be a very long (and useless in certain cases) task to contact all websites.
  • Monitor the changes in terms of crawling, indexation, rankings, traffic and links.

How did we proceed to migrate from a technical point of view?

Massive redirects at scale

We started by checking the capacity of our redirector farm to treat a lot of HTTP(S) redirects and we ensured we were able to do reverse proxy caching of 301 responses for future responses.

Scaling up our infrastructure is easy because we can boostrap new machines with a chef role and machines become quickly able to serve extra requests, that is the power of infrastructure automation!


We started by adding to our plateform SSL certificates and deploy them accross all our delivery nodes.

After that, we added in the HSTS browsers preload lists to register this domain as a full HTTPS one: at a member level, it makes the website faster avoiding to have server redirects extra round-trips, i.e. browser calls HTTPS URLs instead of HTTP ones.

The next step consisted in serving the website using an HTTP Host header with value

From our load balancers/reverse proxy cache levels, we had before migration:

  • routed to our application backends farm
  • routed to our redirector backends farm

So, the steps to serve were:

  • keeping serving with application backend farm
  • routing to application backend farm at a reverse proxy level (no incoming traffic for the moment)
  • decreasing in advance and DNS TTL, then updating to point to our application infrastructure IPs
  • purging the reverse proxy on
  • routing to our redirectors
  • purging

This is how it behaved during migration:

1. => 200, => 301 to
2. => 200, => 200 (during few minutes)
3. => 301 to => 200

How did Google react in terms of crawling?

Right after the migration, Google crawled massively the pages on the domain and he slowed down once they have all been discovered. We’ve now recovered the same crawl volumes as we used to have before the migration.

Crawl volume migration Source: Botify

As predicted, Google’s crawl on is decreasing with time but will certainly never stop because there will always be some remaining websites linking to That’s why redirects should always stay active on

How did Google react in terms of indexation?

  • Despite the redirects, some URLs of and were indexed & positioned in Google at the same time.

Indexation migration

  • During a short period, we also had some URLs of our old platform that disappeared more than 1 year ago back in the search results! And also some URLs of our mobile website appearing in Google’s Desktop results.

Indexation issues migration

  • It took 1 week to get our sitelinks back on the brand name.

Sitelinks BlaBlaCar

  • We now have all new URLs indexed in Google. There are still a lot of URLs in Google’s index because it requires time to clean them.

Volume indexation Google

Impact in terms of ranking?

  • On our top axis pages, it took about 3 weeks to get everything back to normal on keywords “ridesharing + city” (e.g. covoiturage paris) & “ridesharing + axis” (e.g. covoiturage paris nantes).

Rankings covoiturage Source: Myposeo

  • Same thing for axis only (paris nantes), we even get better results after the migration:

Rankings axis Source: Myposeo

Impact in terms of traffic?

  • SEO traffic on the whole website didn’t decrease during the migration, which is definitely the most satisfying result we could encounter.

Traffic migration Source: Botify

  • SEO traffic on city & axis pages actually decreased the 2 weeks after the migration because of the loss of rankings on some queries, but traffic on those pages get back to its normal growth tendency.

Traffic axis migration


We were pretty confident about that migration but we actually didn’t expect so many (strange) moves in Google’s results. Of course you can always make some assumptions why it behaves this way, but you actually have no clue of what is exactly going to happen.

The lesson is that even if you do the maximum of required optimizations, you always have to expect some disturbances in your SEO when you do a website migration. Monitoring the changes with data is the best way to understand what’s really going on and react if things don’t go the right way.

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