crt.sh vs massdns: Side-by-Side Comparison (2026)
Features, pricing, ratings, and pros & cons — compared head-to-head.
crt.sh is a free external attack surface management tool. massdns is a free external attack surface management tool. Compare features, ratings, integrations, and community reviews side by side to find the best external attack surface management fit for your security stack.
CST VerdictBased on our analysis of NIST CSF 2.0 coverage, core features, integrations, company size fit, here is our conclusion:
Security teams doing threat intelligence or domain monitoring should use crt.sh as a free, fast way to spot certificate issuance anomalies that signal domain takeover or phishing campaigns before they scale. Certificate Transparency logs index roughly 15 billion certificates, giving you real-time visibility into what's been legitimately issued against your domains and competitors' infrastructure. Skip this if you need automated alerting or integration into your SIEM; crt.sh is a lookup tool, not a monitoring platform, and catching malicious certificates requires manual checks or custom scripting.
Penetration testers and security researchers running subdomain enumeration campaigns will get the most from massdns; its multi-threaded stub resolver processes 350,000+ queries per second, making it the fastest option for bulk DNS reconnaissance at scale. The 3,417 GitHub stars reflect actual adoption in red teams, and the free pricing means zero friction for integration into custom reconnaissance pipelines. Skip this if your team needs a managed, point-and-click subdomain discovery tool; massdns requires command-line comfort and assumes you're building automation around raw DNS data.
