Other · Yandex
YandexImageResizer user agent, IP ranges and robots.txt
YandexImageResizer is Yandex's other. It identifies itself with the YandexImageResizer user-agent token, honors robots.txt according to its operator, and can be verified by reverse DNS (yandex.ru, yandex.net, yandex.com).
- Operator
- Yandex
- Reviewed
- September 2026
- Sources
- 1
- Operator
- Yandex
- User-agent token
- YandexImageResizer
- Purpose
- Other
- robots.txt token
- YandexImageResizer
- Honors robots.txt
- Yes, per the operator
- Published IP ranges
- No official range file
- Verification
- 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.
- Reverse DNS suffix
- yandex.ru, yandex.net, yandex.com
- Full user-agent example
- Mozilla/5.0 (compatible; YandexImageResizer/2.0; +http://yandex.com/bots)
Block or allow YandexImageResizer in robots.txt
User-agent: YandexImageResizer
Disallow: /User-agent: YandexImageResizer
Allow: /Verify a request is really YandexImageResizer
Anyone can put YandexImageResizer 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>What YandexImageResizer does
Yandex operates YandexImageResizer, which its robot list describes only as a mobile devices robot. It is controlled with the YandexImageResizer robots.txt token, and Yandex states it takes general robots.txt rules into account. Verify a request by reverse DNS to a host ending in yandex.ru, yandex.net or yandex.com, confirmed with forward DNS, or with the Yandex Webmaster IP check tool.
Requests from this robot carry the user agent Mozilla/5.0 (compatible; YandexImageResizer/2.0; +http://yandex.com/bots), with 2.0 as the documented version. Yandex's entire description of what it does is the phrase mobile devices robot. The documentation gives nothing further, so the name is the only hint at its function, and this registry does not expand on it. Yandex does not document which URLs it requests, how often it visits, or whether it executes JavaScript.
Yandex states that YandexImageResizer takes general robots.txt rules into account, so a Disallow under User-agent: * applies to it, and a group addressed to User-agent: YandexImageResizer controls it on its own. Because Yandex does not say what the robot's fetches are used for beyond the words mobile devices robot, the documentation cannot tell you what a block will change. The one certain effect is that the robot stops requesting the disallowed paths. Site owners who want to keep every Yandex service working should leave it allowed; those who block unexplained robots by default can disallow it and watch for any effect.
Operator note. It takes into account the general rules in robots.txt. Yandex gives no description beyond 'Mobile devices robot.'
Common questions
- What does YandexImageResizer do?
- Yandex's documentation describes it only as a mobile devices robot and gives no further detail. The user agent string is Mozilla/5.0 (compatible; YandexImageResizer/2.0; +http://yandex.com/bots). Anything beyond that, including what it does with the pages or images it fetches, the operator does not document.
- Should I block YandexImageResizer?
- Yandex does not document what blocking it changes, because the robot's description is limited to mobile devices robot. It respects robots.txt, including general rules, so a Disallow under User-agent: * or under its own token keeps it out. If you rely on Yandex services for mobile users, allowing it is the cautious choice; otherwise the documentation gives no reason either way.
- How do I verify YandexImageResizer?
- Do a reverse DNS lookup on the requesting IP; a real Yandex robot resolves to a host name ending in yandex.ru, yandex.net or yandex.com. Then do a forward lookup on that host name and confirm it returns the original IP. Yandex Webmaster also has an IP address check tool. Yandex's documentation gives no IP range file for this robot.
Sources
The operator documentation used for this entry. Recorded review date September 2026; consult the linked pages for current policy and compare them with this dated snapshot.
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.