🤖 Overview

SeznamBot is a web crawler operated by Seznam.cz, a Czech internet company that operates the largest search engine in the Czech Republic. Its primary purpose is to index web pages for Seznam's search engine, Vyhledávání, and related products such as the Seznam.cz portal and Firmy.cz business directory. The bot collects content to improve search result relevance and to provide additional services like news aggregation and map data through Mapy.cz.

🌐 Technical Behavior

SeznamBot follows standard crawl patterns, starting from a seed list of URLs and then discovering links within fetched pages. According to official documentation from Seznam, the bot respects the robots.txt protocol and also supports the robots meta tag and X-Robots-Tag HTTP header. The crawler uses the HTTP/1.1 and HTTP/2 protocols and typically identifies itself with the User-Agent string "SeznamBot/3.2" (with version numbers varying). Its requests originate from IP addresses in the range 77.75.72.0/24 and 77.75.73.0/24, registered under the Seznam.cz ASN (AS43757). The crawl frequency can be aggressive, often requesting multiple pages per second from a single domain, but it does not exceed rates that would normally overload a well-configured server. SeznamBot also supports conditional GET requests using If-Modified-Since and ETags to reduce bandwidth usage.

📋 robots.txt Compliance

SeznamBot fully honors robots.txt directives, as confirmed by Seznam's official webmaster guidelines. It also respects Crawl-delay directives if specified. Documentation from Seznam states that the bot reads the robots.txt file once per site per crawl session and caches it for the duration of the crawl. There are no documented cases of SeznamBot ignoring disallow rules, and it is considered a well-behaved crawler.

🔍 Detection Indicators

The primary User-Agent string is "SeznamBot/3.2", though legacy versions such as "SeznamBot/1.0" may still appear. Additional identifying headers include "From: [email protected]" in the From header and "Accept-Language: cs, en". The bot also sends a "Referer" header pointing to the original URL being crawled. Behavioral fingerprints include a high frequency of request bursts separated by longer idle periods and a consistent pattern of visiting only pages with text/html content types.

📊 Data Usage

The collected data is used to build and update the search index for Seznam.cz's search engine, including full-text indexing, keyword extraction, and link analysis. Additionally, content may be used for Seznam's Mapy.cz geolocation services and Firmy.cz business listings. Seznam does not publicly state that the data is used for AI training as of 2025, but it does power their Seznam semantic search algorithms.

⚙️ Rate Limiting Policy

Because SeznamBot can generate high request volumes — sometimes exceeding 100 requests per minute on popular sites — administrators often rate-limit it to prevent server strain. A threshold-based blocking policy (e.g., limiting to 10 requests per second) is recommended based on documented patterns, allowing legitimate indexing while protecting server resources.

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