🤖 Overview

a6-indexer is a web crawler operated by A6 Technologies, a private company based in Beijing, China, that specializes in large-scale web data extraction for artificial intelligence model training. First publicly identified in server logs in January 2022, its explicit purpose is to index publicly accessible web pages to feed into A6's proprietary large language model (LLM) and vertical search engine.

🌐 Technical Behavior

The crawler employs a distributed fleet of headless Chromium browsers running on Amazon Web Services EC2 instances (primarily in us-east-1 and eu-west-1 regions) and Google Cloud Platform (us-central1). It sends HTTP/1.1 and occasionally HTTP/2 requests at a sustained rate of 5 to 10 requests per second per IP address, with a crawl interval of 2 to 5 seconds between pages. The bot executes JavaScript to render dynamic content and follows internal redirects. Known IP ranges fall under Amazon AS16509 and Google AS15169.

📋 robots.txt Compliance

According to A6's official crawler policy published at https://a6.ai/crawler-policy, a6-indexer fully honors robots.txt Disallow directives. Third-party tracking repositories on GitHub (e.g., https://github.com/ai-crawler-tracker/observations) document isolated incidents where the bot temporarily disregarded rules due to cached queues, but A6 states they rectify such issues upon notification within 48 hours.

🔍 Detection Indicators

The primary User-Agent string is a6-indexer/1.0 (with a Mozilla/5.0 compatibility token). Secondary strings include a6-indexer/2.0 and A6Bot/1.0. The bot does not send a custom X-Robots-Tag header or special identification headers; it is identified solely by the User-Agent field. No CVE entries exist as the crawler is not malicious.

📊 Data Usage

Collected data is used exclusively for training A6's conversational AI assistant "A6 Assistant" and improving the company's internal web search index. A6 claims compliance with the EU General Data Protection Regulation (GDPR) by anonymizing collected content and offers an opt-out mechanism at https://a6.ai/opt-out.

⚙️ Rate Limiting Policy

Because a6-indexer generates high request volumes that can degrade performance on smaller hosting environments, webmasters commonly rate-limit it to 3 requests per second or block it entirely after exceeding 1,000 requests per hour. This threshold-based blocking is a standard protective measure that recognizes the crawler's legitimate purpose while safeguarding server resources.

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