Censys Has a Free API — The Shodan Alternative for Internet-Wide Scanning

Everyone knows Shodan. But Censys is the quiet alternative that security researchers often prefer — and it has a generous free API tier. Censys scans the entire IPv4 address space and indexes every TLS certificate. 400 million+ hosts. 7 billion+ certificates. Updated continuously. Why Censys Over Shodan? A security team needed to find all instances of a specific TLS certificate across the internet — a certificate that had been compromised. Shodan couldn't search by certificate fingerprint effectively. Censys found 2,400 hosts using that exact cert in under 3 seconds. Each tool has strengths. Censys excels at certificate intelligence and structured queries. Get Your Free API Key Sign up at search.censys.io Go to Account → API → get your API ID and Secret Free tier: 250 queries/month Search for Hosts \`python import requests from requests.auth import HTTPBasicAuth API_ID = "your-api-id" API_SECRET = "your-api-secret" auth = HTTPBasicAuth(API_ID, API_SECRET) def search_hosts(query, per_pa