Domain Structure for Japan: Subdirectory, Subdomain or .co.jp

Before any Japanese content gets written, someone has to decide where it lives: a subdirectory on the existing domain, a subdomain, or a Japanese ccTLD. The decision is usually made in an hour, rarely revisited, and expensive to reverse.

Here is the reasoning we use, and the two Japan-specific facts that change it.

The short answer

Use a subdirectory on your main domain — example.com/ja/ — unless you have a specific reason not to. For most foreign companies entering Japan, the authority already built on the main domain is the single largest asset available, and a subdirectory is the structure most likely to inherit it in full.

The exceptions are real, but we think they are narrower than usually claimed.

The three options

Structure	Inherits domain authority	Local trust signal	Operational cost
example.com/ja/ Subdirectory	Fully	Weakest	Lowest. One property, one CMS, one team.
jp.example.com Subdomain	Partially, in practice	Weak	Medium. Often a separate stack, which is partly why it gets chosen.
example.co.jp Japanese ccTLD	Not at all — starts from zero	Strongest	Highest. Separate domain, separate authority to build, separate everything.

Many guides stop there. Two Japan-specific details change the calculation.

Fact one: .co.jp is not something you can simply buy

.co.jp is restricted. It is available only to companies registered in Japan, including foreign companies registered there, and a company may in principle hold one of them. You cannot register a portfolio, and before your Japanese entity exists you can only take a provisional registration, which lapses unless the company is registered within six months.

That restriction is a large part of why the domain carries weight with Japanese audiences. A .co.jp address is a statement that a registered Japanese company stands behind the site, and many readers treat it accordingly — particularly in B2B, where the reader is checking whether you are a real counterparty.

The unrestricted alternative, plain .jp, is open to anyone with an address in Japan. It looks Japanese, but we think it carries little of the same signal. If the reason for choosing a Japanese domain is trust, .jp is unlikely to deliver it.

Fact two: the trust signal and the ranking signal are different things

The other half of trust in this market is who is named on the page — see named supervision in Japanese YMYL.

These often get conflated, and separating them settles much of the argument.

• For ranking, a subdirectory on an established domain is usually the stronger position. You start with authority rather than building it.
• For trust, .co.jp is stronger — but that signal is read mainly by a human at the evaluation stage, not by a crawler at the ranking stage. It affects whether the inquiry is sent, not whether the page is found.

So, in our view, this is a sequencing question, not an either-or question. Rank first on the subdirectory. Add the .co.jp later for the corporate presence, once the entity exists and there is something to put on it. Running both is common in Japan, and does not require choosing.

When a separate Japanese domain makes sense

• You already have one with history. If a Japanese subsidiary has been running example.co.jp for years, it has probably accumulated links, brand queries and index history. Migrating that into a subdirectory usually destroys more than it gains.
• The Japanese business is genuinely separate — different product, different company, joint venture. Then it is not a localization question at all.
• Your main domain carries a penalty or a reputation problem. Rare, but it inverts the logic.

Note what is not on that list: “Japanese users prefer .co.jp.” Many do notice it, and it helps at the point of evaluation — but it is not a reason to give up the authority you already have before you have any Japanese content at all.

hreflang, and the three ways it goes wrong

Whatever structure you choose, the Japanese pages need to declare themselves properly.

1. Use ja unless you genuinely mean Japan-the-country. ja targets the Japanese language; ja-JP targets Japanese speakers in Japan. Many companies want the former and write the latter without deciding.
2. Annotations must be reciprocal. If the English page points to the Japanese one, the Japanese one has to point back. One-directional hreflang is ignored, and it is the most common implementation error we find.
3. Every set needs to include itself, and a single x-default should point at the page for users you have not otherwise covered.

Avoid redirecting by IP address

Automatically sending Japanese visitors to the Japanese page sounds helpful but tends to cause two problems.

It breaks crawling — Google predominantly crawls from US IP addresses, so an IP redirect can mean your Japanese pages are never seen from the crawler’s position. And it removes the user’s choice, which can annoy the bilingual buyer who deliberately opened the English page to check a specification.

Suggest, do not redirect. A dismissible banner offering the Japanese version, with the choice remembered, usually does the job without either cost.

A decision in four questions

Once the structure is settled, the next decision is what goes on it first. That sequence is in keyword research in Japanese.

1. Do you already own a Japanese domain with history? If yes, keep it and improve it. Stop here.
2. Is the Japanese business the same business? If not, use a separate domain.
3. Can your CMS host a Japanese subdirectory without a rebuild? If yes, use it. If not, weigh the engineering cost honestly — a subdomain is the usual compromise, and we think it is an acceptable one.
4. Do you have a registered Japanese entity? If yes, register the .co.jp anyway for the corporate site and for the address on your materials. It is cheap, and each company can hold only one.

Common questions

Does hosting in Japan help rankings?

Not directly. It can help page speed for Japanese users, which is worth having on its own terms. Choose it for performance, not for ranking.

Should the Japanese URLs be in Japanese characters?

Usually no. Encoded Japanese URLs become unreadable when copied into a document or a chat message, which matters in a market where the URL frequently gets pasted into an internal proposal. Latin slugs travel better.

We have both a .co.jp and an English site. Which gets the content?

In most cases, whichever already has Japanese search history. Check Search Console, not the org chart, before deciding.

Can we move later?

Yes, with redirects, and it usually costs you a recovery period. Better to spend an extra week on the decision than a quarter on the migration.

Working on Japan?

Nihongo Search is published by Amanaut, Inc., a small Japanese SEO and content company in Tokyo working with companies entering the Japanese market. Structure comes before content, and in our view it is the cheapest thing to get right. The full sequence is in our Japan market-entry SEO guide. More about how we work.

Last reviewed: October 2026.