When it comes to ranking on Google, a subdomain (blog.example.co.uk) and a subfolder (example.co.uk/blog/) start on an equal footing: Google's John Mueller has said so more than once, and in our test on 15 UK searches 7 organic results out of 127 were on a subdomain. The difference lies elsewhere: for crawling, robots.txt, Search Console and the site name, a subdomain is a separate host, in other words a second site to manage and grow.
The question nearly always comes up at the wrong moment.
When the blog is already running on HubSpot, the shop on a different platform from the website, the hotel's booking engine on the supplier's server.
And on page one of Google UK for "subdomain vs subfolder" the answers come from tool vendors, agencies and forums (Semrush, Impact Plus, Weglot, Embarque, Reddit and a Stack Overflow thread from 17 years ago), several of them dated: Semrush's is from November 2023, Search Engine Journal's from February 2021.
The mistakes we see most often are three:
- believing the subdomain is penalised, and rebuilding everything for nothing;
- believing it's identical to a subfolder, and leaving it with no links, no robots.txt and outside Search Console;
- migrating for SEO reasons, expecting a jump in traffic that the documented cases don't show.
On an Italian outdoor equipment e-commerce site we work on, the shop lives on a subdomain. Between May and August 2026 it collected 82 organic clicks against 4,484 for the main domain, 1.8%, with an average mobile position of 13.3 against 5.2. The full table is in our guide on how to build an SEO-friendly website.
So should you avoid subdomains?
No. On the day we ran the test, developers.google.com was first for "what is seo" on Google UK, and support.apple.com was second for "how to back up iphone".
In this guide you'll find:
- what really changes for Google between subdomain and subfolder, with the official pages;
- our test on 127 UK results, search by search;
- the four cases where a subdomain is the right choice;
- how to bring an external blog into a subfolder without changing platform;
- what to expect from a migration and five checks for a subdomain that stays.
Let's start.
What a subdomain is and what a subfolder is (it all depends on which side of the domain they sit)
A subdomain is a prefix that sits before the domain and is set up in the DNS: in blog.example.co.uk the subdomain is "blog". A subfolder is a path that sits after the domain, on the same host: in example.co.uk/blog/ the folder is /blog/.
"www" is a subdomain too, the most common of all.
For readers the difference is almost invisible. For Google's infrastructure it isn't: every hostname is a site of its own for crawling, and nearly all the practical consequences follow from that. We've set them out below.
| Aspect | Subdomain (blog.example.co.uk) | Subfolder (example.co.uk/blog/) | Source |
|---|---|---|---|
| Crawl budget | Separate: Google treats every unique hostname as a site | Shared with the rest of the domain | Google, crawl budget management |
| robots.txt | Needs its own file on the host | The domain's file applies | Google, robots.txt specification |
| Search Console | Included in the Domain property, excluded from the main site's URL-prefix property | Included in both | Search Console Help |
| Site name in results | Can have its own | Uses the domain's: not supported at subdirectory level | Google, site names |
| Google Analytics 4 | Check the cookie domain, or self-referrals appear | No extra configuration | Analytics Help |
| Set-up | A DNS record, even pointing to another server | Same server, or a reverse proxy | Cloudflare |
| Country versions | Easy to set up, servers in different locations; the URL doesn't show whether "de" means language or country | Low maintenance, a single host and a single server location | Google, multi-regional sites |
Our own site, incidentally, uses subfolders for languages too: this article sits under /blog/ and its Italian original under /it/blog/. The other parts of an address, from protocol to fragment, are explained in our guide to URL structure.
What Google says (it treats them the same, but not as the same site)
Google says the choice makes no difference to rankings, and it has been saying so for more than ten years. In 2012 Matt Cutts, then head of the webspam team, described the two options in a Google video as roughly equivalent.
In 2017 Google's John Mueller said in another video that web search is fine with both subdomains and subdirectories, and advised choosing a structure you can keep for the long term.
In 2018, in a hangout reported by Search Engine Journal, he added the sentence hardly anyone quotes: "In general, we see these the same. I would personally try to keep things together as much as possible."
In other words: for rankings it's the same, but he would keep everything together.
And why, if it's the same?
The answer is in the technical documentation. The page on crawl budget, updated in July 2026, says that www.example.com and code.example.com are treated as separate sites with separate crawl budgets, and that every site starts with the same default, conservative crawl capacity limit, which Google raises over time if the server responds well.
So a new subdomain starts from that initial limit even if the main domain has been crawled every day for years.
We've already covered the consequence for the site name shown in results in our article on domains and SEO: news.example.com can have its own, example.com/news can't.
The practical point is this: Google doesn't penalise a subdomain, but it doesn't give it anything for free either. What ties it to the main domain is internal links and the brand, not the address.
The test: how many UK results sit on a subdomain (7 out of 127)
On UK first pages, 5.5% of organic results sit on a subdomain: that's what we measured on 10 October 2026 across 15 searches from different sectors. In Italy, the same test a day earlier gave 14.6% (19 out of 130).
Here's the method, so anyone can repeat it. Using DataForSEO we pulled the top 10 organic results on Google UK, on mobile, for each search. We counted organic results only, so no AI Overviews, recipe cards or local results, and we classed as a subdomain every host other than www and the bare domain, reading domains according to the Public Suffix List (so a GOV.UK service such as find-government-grants.service.gov.uk counts as a domain of its own). The total is 127 and not 150 because many SERPs show fewer than ten organic results.
| Search | Organic results | On a subdomain | Host (organic position) |
|---|---|---|---|
| how to register as self employed | 8 | 0 | none |
| tiramisu recipe | 8 | 0 | none |
| best running shoes | 9 | 0 | none |
| boiler upgrade scheme | 8 | 0 | none |
| what is seo | 7 | 2 | developers.google.com (1), en.wikipedia.org (5) |
| switch energy supplier | 9 | 1 | help.moneysavingexpert.com (5) |
| car leasing | 10 | 0 | none |
| excel course online | 8 | 1 | learn.microsoft.com (2) |
| how to back up iphone | 7 | 2 | support.apple.com (2, 5) |
| first time buyer mortgage | 9 | 0 | none |
| car insurance | 10 | 0 | none |
| how to make a website | 8 | 0 | none |
| self assessment tax return | 8 | 1 | en.wikipedia.org (7) |
| check mot history | 9 | 0 | none |
| things to do in london | 9 | 0 | none |
| Total | 127 | 7 (5.5%) | 3 in the top three |
7 results out of 127 sit on a subdomain. 5 searches out of 15 have at least one.
In the top three positions subdomains take 3 places out of 45, 6.7%: slightly more than their share of the total.
Unlike the Italian test, Wikipedia does show up here, twice, on en.wikipedia.org. Take it out and the UK figure falls to 5 results out of 125.
So who are they?
Of the three families we found in Italy, only two show up in the UK:
- help centres and documentation: developers.google.com, learn.microsoft.com, support.apple.com twice and help.moneysavingexpert.com, 5 results in all;
- encyclopaedia: en.wikipedia.org twice, 2 results;
- quote tools, blogs and shops: none. The comparison sites that in Italy run on subdomains (preventivo.prima.it, assicurazioni.segugio.it) are replaced in the UK by players working in subfolders: comparethemarket.com/car-insurance/, gocompare.com/gas-and-electricity/, uswitch.com/gas-electricity/.
Our reading: when a subdomain reaches the top three, there's a brand behind it that people search for by name (Google, Microsoft, Apple). The address doesn't seem to hold them back. Fifteen searches are a small sample and prove no cause, but they're enough to disprove the idea that a subdomain can't rank high, and to show that in the UK almost nobody below that brand level is trying.
Why a subdomain struggles on a small site (and where the work gets lost)
On a domain with little brand recognition, a subdomain is a second site starting from scratch: links to earn, crawling to win, one more property to keep an eye on.
And nearly always nobody has budgeted the hours to make it grow.
Three situations we find in audits:
- the shop cut off from the site: this is the outdoor e-commerce case mentioned at the start, where the subdomain had 4,718 impressions against 190,200 for the main domain over the same period;
- the blog on an external platform left on default settings: in a check of 18 Italian agency sites on HubSpot, the only 2 without a canonical on the home page were blogs on a subdomain (the details are in our guide to HubSpot SEO);
- the hotel's booking engine on the supplier's subdomain, fronted by a five-page website: the pages that could rank simply don't exist. We cover this in our guide to hotel SEO.
The cost isn't a penalty.
It's pages that nobody links to, nobody checks and nobody updates, because they live "somewhere else".
Do you have a blog or a shop on a subdomain that isn't growing?
In the case you've just read, the shop collected 1.8% of the main site's clicks. Before deciding whether to migrate, we look at both hosts' data in Search Console and tell you whether to move it, link it better or leave it where it is.
Book a strategy consultationWhen a subdomain is the right choice (four cases where separating really helps)
A subdomain makes sense when the separation serves something other than SEO: a different server, a different platform, different authors or a different market.
1. Applications and private areas. app.example.co.uk, the customer area, the login. They don't need to rank, and here a separate crawl budget is an advantage: a traffic spike on the application doesn't slow down crawling of the website.
2. Third-party platforms that can't be mounted on the same host. Help centres, communities, booking engines, SaaS shops. If a reverse proxy isn't practical (more on that in the next section), a subdomain is the only clean route. The UK test bears this out: every subdomain in the top results that wasn't Wikipedia was a help centre or a documentation hub.
3. Content by other authors hosted by your brand. In Italy this is the model of blog.giallozafferano.it: a WordPress platform where independent food bloggers run their own blogs, kept separate from the editorial team's recipes.
Here, though, there's a line drawn in writing. Google's spam policies, updated in August 2026, target third-party content published on a host site mainly because of that host's already-established ranking signals. And in the section on policy circumvention they explicitly list using existing or creating new subdomains and subdirectories to keep violating them.
In other words: moving a penalised section onto a subdomain won't save it. How to recognise a penalty is explained in our guide to Google penalties.
4. Country sites with different servers, teams or offers. In Google's table on multi-regional sites, one of the pros of subdomains is the option of servers in different locations. In Italy, the estate agency network Tecnocasa uses one subdomain per branch, and it works because every branch has its own listings: we cover it in our guide to franchise SEO.
For plain translations of the same site a subfolder means less maintenance, and it's the choice we made ourselves. Either way you need hreflang, and when the versions become separate domains the picture changes again: see our article on why multiple domains are a problem for SEO.
Test environments are a case apart. A staging subdomain should be password-protected: a disallow in robots.txt blocks crawling, not indexing, and a blocked URL can still appear in results if someone links to it.
A blog on an external platform: how to move it into a subfolder without changing CMS
If the subdomain only exists because the blog runs on another platform, there's a third way: a reverse proxy, a server that answers on example.co.uk/blog/ and fetches the pages from wherever they actually live.
The Cloudflare blog explains well why you need one: DNS only works at domain level, so a CNAME record can point blog.example.co.uk to another server, but it can't do the same for example.co.uk/blog. For a subfolder you need a rule on the server, for example a location block in NGINX, or a tool such as Cloudflare Workers.
And once the proxy works, is that it?
No, there are three checks that almost always get skipped:
- canonicals and sitemap must point to the subfolder URL, not the one on the original subdomain;
- the old subdomain has to be redirected with a 301 page by page, or two copies of the same blog will exist;
- internal links from the blog to the site, and the other way round, need rewriting to the new path.
The price is a few hours of development and one more point of failure to watch: if the proxy goes down, the blog goes down.
Moving a subdomain into a subfolder: what to expect (the Mention case)
A migration from subdomain to subfolder, on its own, moves traffic but doesn't multiply it. The most cited case was documented by Ahrefs: Mention moved its blog into a subfolder in January 2016, every page lost traffic and then regained roughly the same amount. The growth came later, with new content.
GitHub also moved from github.com/blog to blog.github.com and then to github.blog, with too many other changes along the way to credit anything to the address alone.
The rule we draw from this: you migrate to make management simpler, not to gain rankings.
If you decide to do it, this is the order we follow:
- map old URLs to new ones one by one, including pages nobody looks at any more but that have external links;
- direct 301 redirects, with no chains, to be kept according to Google for at least a year;
- internal links, canonicals and sitemap updated on the same day;
- both hosts monitored in Search Console until the old pages drop out of the index.
In its site move guide, Google warns that for a small or medium site it can take a few weeks for most pages to move. The full checklist is in our article on rebranding and SEO migration, and if the move happens as part of a redesign, our guide to SEO for a website redesign applies too.
If the subdomain stays: five checks to run today
If the subdomain has a reason to exist, it needs managing as the separate site Google considers it to be. The five checks we run first:
- a Domain property in Search Console: it covers all subdomains and protocols in a single dashboard, while a URL-prefix property leaves them out. How to set it up is explained in our guide to Google Search Console;
- robots.txt on the subdomain: the rules only apply to the host, protocol and port the file is fetched from, so the main domain's file doesn't count;
- links from the menu and footer of the main site to the subdomain and back, with descriptive anchors: it's the only thing holding the two halves together (the criteria are in our guide to internal links);
- the cookie domain in Google Analytics 4: if subdomains use different cookie domains, self-referrals appear and traffic gets attributed wrongly;
- WebSite structured data on the subdomain, because the site name in results is assigned at that level too: the right markup is in our guide to schema markup.
Frequently asked questions about subdomains and SEO
It depends: not automatically because of the address. Google crawls it as a separate site, with its own crawl budget, and the link to the main domain comes through internal links and brand recognition. In our 10 October 2026 test on Google UK, every subdomain in the top three results belonged to Google, Microsoft or Apple.
No. Google's John Mueller said in 2017 and 2018 that subdomains and subfolders are both fine for search. In our test on 15 UK searches, 7 organic results out of 127 were on a subdomain and 3 were in the top three positions.
No, almost never. The blog is there to bring visibility to the commercial pages, and in a subfolder it shares their host, crawling and internal links. A subdomain only makes sense if the blog platform can't be mounted on the same host and a reverse proxy isn't practical.
Yes. The file's rules only apply to the host, protocol and port it is fetched from: the robots.txt on example.co.uk doesn't apply to blog.example.co.uk.
It depends: with the same team and the same server a subfolder means less maintenance, and it's the choice we made on our own site. A subdomain makes sense when the country versions have different servers, teams or offers. Either way you need hreflang.
No, not on its own. In the Mention case documented by Ahrefs, pages lost traffic after the migration and then regained about the same amount. The growth came later, with new content.
To sum up:
For rankings, subdomain and subfolder start on an equal footing.
For crawling, robots.txt and Search Console, a subdomain is one more site.
In the test, 7 UK results out of 127 sit on a subdomain, 3 of them in the top three.
You separate for a technical or content reason, not for SEO.
You migrate to simplify, not to gain rankings.
One thing the industry rarely says: the real choice isn't between two addresses, it's between two budgets. A subdomain that works has someone who updates it, links it and monitors it in Search Console as a separate site, and the brands that rank well with a subdomain in our test (Google, Microsoft, Apple) have those resources. If that person isn't there, the subfolder wins not because Google prefers it, but because it's the only one that will be looked after. If you want to know which of the two routes holds up on your site, it's one of the first checks in our SEO consultancy.
Until next time!
