YandexOntoDB
Yandex operates YandexOntoDB, documented as the information card robot. Site owners control it with the robots.txt token YandexOntoDB, and Yandex says it follows general robots.txt rules. Verification is by reverse DNS to a hostname ending in yandex.ru, yandex.net or yandex.com with forward DNS confirmation, or with the Yandex Webmaster IP check tool; Yandex publishes no IP range list.
Mozilla/5.0 (compatible; YandexOntoDB/1.0; +http://yandex.com/bots)What YandexOntoDB does
YandexOntoDB identifies itself in logs as Mozilla/5.0 (compatible; YandexOntoDB/1.0; +http://yandex.com/bots). Yandex's robot list gives it a single-line description, the information card robot, and nothing more. The documentation does not say what an information card is, which pages the robot fetches, how often it visits, or whether it executes JavaScript. A site owner can therefore only tell from the user-agent string that the request belongs to this Yandex robot rather than to another Yandex robot.
The entry files YandexOntoDB under search engines, and Yandex states that it takes general robots.txt rules into account. A site owner can address it directly with the User-agent token YandexOntoDB or rely on rules written for all agents. Blocking it withholds the site's pages from whatever information cards Yandex builds with this robot; since the operator does not describe those cards, the entry cannot say more about what is lost. Allowing it lets Yandex use the site's content for that purpose.
To confirm a request, run a reverse DNS lookup on the source IP and check that the hostname ends in yandex.ru, yandex.net or yandex.com, then resolve that hostname forward and make sure it returns the same address. Yandex also provides an IP address check tool inside Yandex Webmaster. Yandex publishes no IP range file for this robot, so DNS and the tool are the only documented methods.
Operator note. It takes into account the general rules in robots.txt.
Controlling YandexOntoDB with robots.txt
Use the token YandexOntoDB in robots.txt. Yandex documents that YandexOntoDB honors robots.txt directives.
User-agent: YandexOntoDB
Disallow: /User-agent: YandexOntoDB
Allow: /Verifying a request is really YandexOntoDB
Anyone can put YandexOntoDB in a User-Agent header. Reverse DNS lookup on the requesting IP must return a host ending in yandex.ru, yandex.net or yandex.com, and a forward DNS lookup of that host must return the same IP. Yandex Webmaster also provides an IP address check tool.
host <request-ip>
# expect a hostname ending in yandex.ru, yandex.net, yandex.com
host <that-hostname>
# expect it to resolve back to <request-ip>Common questions
What does YandexOntoDB do?
Yandex's documentation calls it the information card robot and gives no further description. It does not explain what an information card is, which pages the robot requests, or how often it comes. The user-agent string is Mozilla/5.0 (compatible; YandexOntoDB/1.0; +http://yandex.com/bots).
Should I block YandexOntoDB?
Only if you do not want Yandex using your pages for its information cards. Yandex says the robot takes general robots.txt rules into account, so a Disallow for the YandexOntoDB token or for all agents should hold it back. The docs give no detail on what appearing in an information card means for a site.
How do I verify YandexOntoDB?
Reverse-resolve the requesting IP and confirm the hostname ends in yandex.ru, yandex.net or yandex.com, then resolve that hostname forward and check it returns the same IP. Yandex Webmaster also has an IP address check tool for this. Yandex publishes no IP range list to match against.
Sources
Every fact on this page was checked against Yandex's own documentation, listed below, and re-checked by a second reviewer before publication. Reviewed September 2026.
Related crawlers
This registry documents how operators describe their own bots so site owners can identify and control them. It does not publish third-party IP lists or guess at undocumented behaviour. To see how your own site responds to automated visitors, the bot detection scanner reads a URL's live response and names the protection it finds.