Subdomain indexing

Yandex treats every subdomain as a separate site. That single fact governs everything else: each one is added to the console separately, verified separately, assigned a region separately, and crawled separately.

The two legitimate uses

• Regional subdomains — put the region in the address (spb.example.com) and assign the matching region. Assignment is moderated, and contact information is one of the verification criteria. Yandex says outright: do not use a regional subdomain where the company has no physical office in that region. A subdomain claiming a city it cannot document will fail moderation.
• Language subdomains — use the standard language code (en.example.com), add alternate links between versions, and assign a region such as the United States.

What has to be done per subdomain

1. Follow the general site recommendations — it is a site.
2. Add it to the console and verify it. The verification code from the primary address works, provided you verified that address yourself rather than being granted rights on it.
3. Set its region, so it is eligible for location-dependent queries.
4. Set its crawl rate if needed, since that setting is per site too.

The costs people underestimate

Each subdomain consumes crawl capacity of its own — Yandex names this as a cause of server load spikes and suggests reconsidering whether subdomains are needed at all when logs show most requests going to them. Authority does not pool: five regional subdomains are five sites building their standing separately, not one site with five sections.

Blocking and removal

Both work exactly as for an ordinary site — robots.txt and noindex for blocking, the removal tool with the same prerequisites for removal. Note that a subdomain appearing in search unexpectedly is one of the standard diagnostics recommendations, and staging environments are the usual culprit.