IPQS Proxy Detection API is a service that identifies IP addresses associated with proxies, VPNs, Tor nodes, and other anonymized connections. The service analyzes IP addresses and connection forensics to determine if users are hiding behind spoofed or tunneled connections. The API returns over 25 data points for each lookup to provide risk assessment of connections. It maintains threat blacklists that are updated in real-time to include emerging threats from hijacked computers, open proxies, residential proxies, botnets, data centers, and private VPNs. The service purges retired proxy IP addresses from blacklists to reduce false-positives. The tool can be accessed via API lookup, user dashboard, or CSV file upload. It provides IP reputation scoring that includes detection of residential proxies, datacenter proxies, anonymous proxies, and compromised devices. The service allows users to pass additional data points such as device information, transaction information, email addresses, physical addresses, and phone numbers for enhanced accuracy. IPQS offers customizable scoring settings and custom rules to personalize detection for specific audiences. Machine learning algorithms continuously learn from lookup history to improve detection. The service is designed to identify connections with high probability of malicious intent while minimizing impact on legitimate traffic. Use cases include preventing duplicate and fake user accounts, detecting click fraud and ad fraud, preventing payment and transaction fraud, blocking account takeover attempts, enforcing geographic restrictions, and verifying lead generation data quality.