What is YandexBot MirrorDetector?

YandexBot MirrorDetector is a specialized web crawler developed and operated by Yandex LLC, the company behind Russia's largest search engine. You can learn more about Yandex's crawlers at Yandex.com/bots. This bot is a component of Yandex's web crawling infrastructure, designed specifically to identify duplicate content across the internet.

The bot identifies itself in server logs with the user agent string: Mozilla/5.0 (compatible; YandexBot/3.0; MirrorDetector; +http://yandex.com/bots). This distinctive identifier helps website administrators recognize when this particular Yandex crawler is visiting their site.

Unlike some web crawlers, YandexBot MirrorDetector is focused on analyzing and comparing website structures rather than simply indexing content. It examines the DOM structure, text content, and even HTTP headers to identify websites that may be mirrors or duplicates of one another. The bot employs sophisticated algorithms to detect similarity patterns between websites, helping Yandex maintain a cleaner search index.

Why is YandexBot MirrorDetector crawling my site?

YandexBot MirrorDetector visits your site primarily to determine if your content is original or a duplicate of content found elsewhere on the web. This happens as part of Yandex's ongoing efforts to improve search result quality by identifying and properly handling mirror sites.

The crawler typically visits sites less frequently than Yandex's main indexing bot—you might see it accessing your site only a few times per month. It's particularly interested in comparing your site's structure and content with other similar sites in Yandex's index.

YandexBot MirrorDetector may increase its crawling activity if your site has content that appears similar to other websites, if you've recently launched a new site with content from another domain, or if you maintain multiple versions of your site (such as regional or language variants).

What is the purpose of YandexBot MirrorDetector?

The primary purpose of YandexBot MirrorDetector is to maintain the integrity of Yandex's search index by identifying duplicate content across the web. This helps Yandex deliver more diverse and relevant search results to its users by ensuring that similar or identical content doesn't appear multiple times in search results.

When the bot identifies mirror sites, Yandex can make informed decisions about which version to prioritize in search results. This typically involves selecting the most authoritative version based on factors like publication dates, backlink profiles, and explicit canonical designations.

For website owners, this process can be beneficial as it helps prevent content scraping sites from outranking original content. It also helps consolidate search ranking signals to the canonical version of content when you maintain multiple versions of your site.

How do I block YandexBot MirrorDetector?

YandexBot MirrorDetector respects standard robots.txt directives, making it relatively straightforward to control its access to your site. If you want to block this bot completely, you can add the following to your robots.txt file:

User-agent: YandexBot
Disallow: /

This will block all Yandex bots, including the MirrorDetector. If you want to block only specific sections of your site from being crawled, you can use more targeted directives:

User-agent: YandexBot
Disallow: /private/
Disallow: /members/
Allow: /

Keep in mind that blocking YandexBot may affect your site's visibility in Yandex search results, which could impact traffic from users of this search engine. If your site receives significant traffic from Russia or other regions where Yandex is popular, you might want to consider allowing the bot while using canonical tags to properly manage duplicate content instead of blocking it entirely.

If you're concerned about excessive crawling rather than the crawling itself, you can also implement rate limiting at the server level to control how frequently the bot can access your site without blocking it completely.

YandexBot MirrorDetector