Consolidate The Subdomain Split

One authority pool outranks two half-strength ones split across a subdomain.

Google mostly treats a subdomain as a separate site. blog.yourcompany.com and yourcompany.com/blog sit on the same server, share the same brand, and get written by the same team, but to a crawler they are two different authority pools that never fully merge. Plenty of companies run their blog or help center this way for years without ever asking why the subdirectory pages on their main site outrank the ones on the subdomain. The fix is a migration, not a redesign, and the best documented result of doing it is too big to ignore.

What to do: Move your blog, help center, or resource hub off its subdomain and into a subdirectory of the primary domain, yoursite.com/blog instead of blog.yoursite.com. 301-redirect every old URL to its new subdirectory equivalent, keep the slugs the same wherever you can, and leave the migration alone for a few months before you touch anything else on that content.

Why it works: A subdirectory is legally and technically part of the root domain, so it inherits the whole domain's backlink and trust profile. A subdomain only partially does.

Example: Buffer ran its blog on blog.bufferapp.com for years, then merged it into two subdirectories on the main domain, buffer.com/library and buffer.com/resources. Within months of finishing the move, Buffer's organic sessions across the merged domain roughly doubled, climbing from around 445,000 to about 900,000 a month, according to the migration case study published by the growth agency Foundation.

Walk it through

I ran this against buffer.com in July 2026, seven years after the migration. Here is exactly what came back.

1. Ask the old subdomain where it lives now.

curl -sIL https://blog.bufferapp.com

HTTP/2 302
location: https://buffer.com/resources/
HTTP/2 200

blog.bufferapp.com still resolves. It just does not host anything anymore. Every request to it gets a 302 straight into buffer.com/resources/, which means every backlink still pointing at the old subdomain, and there are hundreds of thousands of them, is now feeding authority to the main domain instead of a separate one. Buffer never had to ask link partners to update anything. The redirect does the work forever.

2. Open the subdirectory that replaced it.

Buffer's /library subdirectory: the same top nav, the same domain, a full blog section living inside buffer.com instead of on a separate subdomain

buffer.com/library is not a stripped-down landing page bolted onto a real product site. It is a complete blog, hundreds of posts deep, sharing the same navigation, the same domain, and the same authority pool as the pricing page and the signup flow two clicks away. That is the entire point of the move. The content did not get smaller. The domain it lives on got more powerful.

3. Confirm it is still the live setup, not a one-time redirect that got abandoned.

Both buffer.com/library and buffer.com/resources return clean 200s today. Buffer split its content in two on purpose, SEO-driven posts in /library, brand and product content in /resources, and kept both inside the main domain rather than letting either drift back to a subdomain. Seven years on, nobody unwound it.

The read

The redirect is the whole migration. Authority does not move from a subdomain to a subdirectory because you added an internal link. It moves because the old URL 301s to the new one and stays that way permanently.
A split domain is two weaker profiles, not one strong one. Every backlink earned by the subdomain was never fully counted toward the main domain's strength. Merging them stops that leak.
Permanence is the tell. A redirect still live seven years later means the company measured the result and never considered reversing it. That is a stronger endorsement than any single traffic chart.

Steal it

Audit where your own content lives. If your blog, docs, or help center sits on a subdomain, that is a second authority profile you are building for no reason. Plan the move to a subdirectory, write 301s for every old URL to its exact new equivalent, keep the slugs, and change nothing else about the content or templates in that same window. You want the domain move to be the only variable, so when traffic shifts you know what caused it. Expect a dip before the recovery. Ranking signals take weeks to reattach to the new path, and panicking mid-migration is how companies talk themselves into reverting a move that was about to pay off.

Defend the same ground on the way in. If a vendor, a help-desk tool, a careers page, a docs platform, only offers you a subdomain by default, ask if it supports a reverse proxy or a subdirectory mount before you sign the contract. And if a team inside your own company wants to spin up a new microsite, push back on putting it on a subdomain out of habit. Every new subdomain is a fresh authority pool starting from zero when it could have been adding to the one you already have.

Gotchas

The dip is real and it comes first. Search engines need time to recrawl and reattach signals to the new URLs. Judge the migration on a multi-month window, not the first two weeks.
Do not bundle it with anything else. A redesign, a slug rename, or a CMS switch happening at the same time as the domain move destroys your ability to attribute the result to the move itself.
Some platforms fight you on this. Certain help-desk and support tools only serve their widget from their own subdomain no matter what you do. Confirm reverse-proxy support before you promise stakeholders a subdirectory migration you cannot actually deliver.