🤖 Overview

Thumbnail.CZ Robot is a legitimate web crawler operated by Seznam.cz, a.s., the Czech internet company behind the Seznam search engine and associated services. Its primary purpose is to capture screenshots (thumbnails) of web pages for display in Seznam’s search result previews, email clients (Seznam Email), and other content aggregation features. The bot was first documented around 2016 and is maintained internally by Seznam’s engineering team to support their proprietary thumbnail generation pipeline.

🌐 Technical Behavior

The bot performs HTTP GET requests targeting any publicly accessible URL, typically using a headless browser (PhantomJS or Chromium-based) to render the full page and capture a PNG screenshot. Crawl frequency is moderate — usually one request per URL, with no repeat visits unless the page content changes (detected via Last-Modified or ETag headers). Requests originate from IP ranges owned by Seznam (ASN 25411, 91.219.219.0/24 and 193.84.16.0/22 confirmed in official WHOIS records). The bot uses TLS 1.2+ and sends a standard Accept header of text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8. It does not follow redirects beyond three hops and respects Cache-Control: no-store directives to avoid caching sensitive pages.

📋 robots.txt Compliance

According to Seznam’s official developer documentation at napoveda.seznam.cz, the Thumbnail.CZ Robot fully respects robots.txt Disallow rules and also honors the X-Robots-Tag: noimageindex HTTP header to skip thumbnail generation for specific pages. Public logs show it obeys both wildcard and path-level exclusions without delay.

🔍 Detection Indicators

The primary User‑Agent string is “Thumbnail.CZ robot” (case‑sensitive), sometimes appended with a version like “Thumbnail.CZ robot 1.1”. Additional identifiers include the From header set to [email protected] and the Accept-Encoding header listing gzip, deflate. Traffic lacks typical browser fingerprint elements such as Sec-CH-UA or JavaScript execution details, making it distinguishable from human visitors.

📊 Data Usage

The captured screenshots are stored temporarily on Seznam’s infrastructure (typically up to 30 days) and served as small JPEG/PNG thumbnails (e.g., 120×90 pixels) in search result snippets and email link previews. No page text, HTML structure, or user‑specific data is retained; the bot discards the rendered content after the image is generated.

⚙️ Rate Limiting Policy

Because the bot can issue multiple rapid requests when scanning a site’s pages for previews, it is rate‑limited to prevent excessive load. Administrators are advised to set a threshold of 10 requests per second per IP from the Seznam ranges; blocking beyond this ensures server stability without permanently banning a legitimate crawler.

ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the bots listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.