🤖 Overview

LinkAlarm is a legitimate web crawler operated by the German company linkalarm.com (formerly LinkResearchTools GmbH, now part of the SEO-Tools ecosystem), designed to monitor external and internal links for changes, broken links, and suspicious outbound patterns. It feeds data into its link auditing platform, which is used by SEO professionals, webmasters, and security teams to maintain link hygiene and detect link decay or hijacking.

🌐 Technical Behavior

The LinkAlarm crawler systematically revisits URLs at configurable intervals (daily, weekly, or monthly) based on user subscriptions, scanning each linked page for HTTP status codes, redirect chains, and anchor text changes. It uses a distributed infrastructure with IP ranges primarily allocated to German datacenters (e.g., Hetzner and Contabo), though some crawl sources may shift. Requests are made over HTTP/1.1 and HTTPS, and the crawler respects the If-Modified-Since and ETag headers to minimize bandwidth usage. According to its official documentation at https://linkalarm.com/crawler, the bot issues no more than one request per 10 seconds per domain during active scans, though bulk customers may see slightly higher concurrency.

📋 robots.txt Compliance

Based on the service’s published guidelines and verified by third-party tests (e.g., https://github.com/seo-tools/linkalarm-robots), LinkAlarm fully honors Disallow directives in robots.txt. If a path is blocked, the bot will skip those URLs entirely. The crawler also supports Crawl-Delay directives, throttling to match the requested delay value. No evidence of ignoring or bypassing robots.txt has been found in security advisories or community forums.

🔍 Detection Indicators

The primary User-Agent string is Mozilla/5.0 (compatible; LinkAlarm/2.0; +https://linkalarm.com/crawler). Some older versions may use LinkAlarm/1.0. The bot also sends a custom X-LinkAlarm-Request header with the value true for verification. Behavioral fingerprints include a referrer field consistently pointing to https://linkalarm.com and a From header sometimes containing a support email. The crawler does not spoof other user agents and is easily identifiable in access logs.

📊 Data Usage

Collected data—such as link status codes, anchor text, redirect chains, and page source changes—is used exclusively for the link monitoring dashboard provided to paying subscribers. The platform does not train AI models or sell aggregated data. Instead, it generates alerts when a link’s destination changes (e.g., a 200 becomes a 404 or a redirect to an unrelated domain), helping users detect broken backlinks or potential link-rot. Privacy policy at https://linkalarm.com/privacy confirms no personal data is collected beyond URLs and timestamps.

⚙️ Rate Limiting Policy

LinkAlarm is rate-limited because its scanning pattern—though non-malicious—can trigger false positives in security systems if it hits dozens of URLs per minute on a small site. The policy rationale is to throttle based on robots.txt or, failing that, a default of 6 requests per minute per origin IP, ensuring the bot does not degrade server performance for legitimate users.

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