<details><summary>Proof-of-work CAPTCHA & anti-spam API</summary>Create and verify challenges to protect forms and APIs without using cookies or user tracking. Supports classification and customizable complexity.</details>
Visit API Website →| Name | ALTCHA API |
| URL | https://altcha.org/ |
| Category | Anti-Malware & Security |
| Source | keploy-public-apis-collection |
| Added | May 30, 2026 |
<details><summary>Look up domain, DNS, IP, and historical WHOIS data</summary>Ideal for threat intelligence and domain investigation tools.</details>
<details><summary>Check URLs against Google’s list of unsafe web resources</summary>Protect users by warning about phishing, malware, and harmful sites.</details>
<details><summary>Check if email addresses have been compromised in data breaches</summary>Help users check if their credentials have been exposed in known …
<details><summary>Detect fraudulent users, bots, and malicious IPs</summary>Prevent fake signups and abuse with fraud scoring, email validation, and proxy/VPN detection.</details>
<details><summary>Scan HTTP security headers for web applications</summary>Analyze websites for TLS, HSTS, CSP, XSS protection, and more.</details>