🤖 Overview

web-sniffer is a web-based HTTP debugging tool operated by an independent developer, launched around 2002 and hosted at web-sniffer.net. It allows users to manually fetch any public URL with customisable request headers—including User-Agent, Referer, and cookies—and view the raw server response, including status codes, headers, and body content. This tool is intended for legitimate debugging, web development testing, and security assessments; it is not an autonomous crawler or search engine bot.

🌐 Technical Behavior

Each request is initiated by a user via a web form; the web-sniffer server then performs an HTTP or HTTPS request to the target URL on behalf of that user. Requests originate from a pool of IP addresses primarily belonging to Hetzner (AS24940) and other German data centres. The tool sends a default User-Agent of Mozilla/5.0 (compatible; web-sniffer/1.0; +http://web-sniffer.net/) but allows the user to override this string arbitrarily. It follows HTTP redirects (default limit 10) and supports custom request methods. The service does not cache or store response data persistently; results are displayed temporarily and discarded after the session. There is no automated crawling logic—each fetch is isolated and user-triggered.

📋 robots.txt Compliance

Because web-sniffer is a manual fetch tool and not a bot that walks links, it does not automatically parse or obey robots.txt directives. The operator recommends that users respect target site policies, but the tool itself provides no built-in robots.txt enforcement. Webmasters who wish to block the service can add a User-Agent rule for web-sniffer/1.0 in their robots.txt, though users can easily change the User-Agent to any other value, so this is not a reliable block.

🔍 Detection Indicators

The primary indicator is the default User-Agent string: Mozilla/5.0 (compatible; web-sniffer/1.0; +http://web-sniffer.net/). The Referer header typically contains http://web-sniffer.net/. The tool often omits common browser headers like Accept-Language and Accept-Encoding, and may add a Via proxy header. Source IPs are generally in the Hetzner range (185.12.xx, 88.198.xx, etc.). The request frequency is variable—depends on how many users submit URLs—but can spike during active use.

📊 Data Usage

Collected data (the server response) is shown to the requester for immediate debugging and is not stored, aggregated, or used for AI training or indexing. The service’s privacy policy states that no personal data is harvested from the target sites. Logs of requests (URL and timestamp) may be retained temporarily for operational monitoring, but response bodies are not logged.

⚙️ Rate Limiting Policy

Although web-sniffer is a legitimate debugging aid, a single user can rapidly submit many URLs, causing repeated requests to the same target. A threshold-based rate limit (e.g., >10 requests per minute from the same IP) is recommended to prevent unintended load, as the tool does not implement any internal rate limiting and can be used for aggressive reconnaissance.

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