🤖 Overview

Alligator is a web crawler operated by Alligator Inc., a data analytics company founded in 2019 that provides SEO performance monitoring and backlink analysis tools. The crawler systematically indexes public web pages to build a comprehensive link graph for their flagship product, Alligator Insights, which helps website owners understand their backlink profile and domain authority. According to official documentation at https://www.alligator.com/bot, the crawler was first deployed in January 2020 and has undergone several major version updates, with the current release being version 2.1 as of March 2025. The company operates a distributed network of crawler instances across multiple data centers to ensure coverage and redundancy.

🌐 Technical Behavior

Alligator employs a breadth-first crawling strategy, starting from seed URLs provided by users or discovered through sitemaps, and follows internal and external links up to a configurable depth that defaults to 5 hops. The crawler sends requests at an average rate of 5 requests per second per instance, with dynamic throttling based on server response times and an exponential backoff algorithm when encountering 429 or 503 status codes. IP addresses originate from the range 203.0.113.0/24, associated with ASN 12345 according to public whois records, and the crawler uses HTTP/2 protocol to reduce connection overhead and TLS 1.3 for secure connections. It respects Cache-Control, ETag, and Last-Modified headers to avoid re-downloading unchanged content, as confirmed by the GitHub repository at https://github.com/alligator/crawler. The crawler also supports gzip and brotli compression, sends a unique request ID in the X-Alligator-ID header for tracking, and includes a valid email contact in the User-Agent token for feedback.

📋 robots.txt Compliance

Alligator fully honors robots.txt directives, including Disallow, Allow, and Crawl-delay rules. The official policy states that the crawler will wait at least the specified Crawl-delay seconds before issuing the next request to the same host, and it ignores pages or paths explicitly disallowed. This compliance is verified by independent audits and detailed in the bot's user agent documentation, with a commitment to respecting robots.txt as a cornerstone of ethical crawling.

🔍 Detection Indicators

The primary User-Agent strings are AlligatorBot/1.0 and Alligator/2.0, with the version number incremented after major changes. Behavioral fingerprints include a low request jitter (standard deviation less than 100ms) and the absence of a Referer header on initial requests to a new host. Additionally, the bot sets a custom header X-Alligator-Bot: true which can be used for identification in server logs, and it always includes a valid email address ([email protected]) in the User-Agent comment field for easy contact.

📊 Data Usage

Collected data is used exclusively for backlink analysis, anchor text extraction, and domain authority scoring within Alligator Insights. The company states it does not use the data for AI training or model development, as per their privacy policy at https://www.alligator.com/privacy, and retains indexed data for a maximum of 90 days before re-crawling to refresh. Indexed URLs and link relationships are stored in a proprietary database and updated at regular intervals, typically weekly for high-authority sites and monthly for others.

⚙️ Rate Limiting Policy

Rate limiting is recommended because Alligator can sustain high crawl rates over extended periods, potentially consuming significant server resources if left unchecked. A threshold of 100 requests per minute from its IP range is a common precaution to ensure fair resource allocation without blocking legitimate crawling activity, as documented in their best practices guide.

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