NULLBLOCKS VS CENSYS
Different tools for a related job.
Censys is an internet-wide search engine — you query it to find hosts, certificates, and services across the entire internet, and it's genuinely good at that. NullBlocks is narrower and more opinionated: point it at a domain and it does the discovery, version fingerprinting, CVE correlation, and dangling-subdomain detection for you, then keeps watching. Different design goal, not a strict replacement.
HONEST COMPARISON
| NullBlocks | Censys | |
|---|---|---|
| Core model | Domain-in, full attack-surface report out | Internet-wide search index you query yourself |
| Version-matched CVE correlation | Built in, automatic | Possible via queries, requires your own correlation work |
| Dangling-subdomain / takeover detection | Built in, automatic | Not a built-in feature — data can support it, logic is on you |
| Free instant report, no signup | Yes | Limited free search; full access is a paid account |
| API/CLI for programmatic access | Not yet — see our FAQ | Yes, a core part of the product |
| Breadth of internet-wide search | Scoped to the domains you give it | Its core strength — query anything, anywhere |
WHEN TO USE WHICH
If you need to search the entire internet for a specific fingerprint, certificate, or exposed service — Censys is built for exactly that, and does it well. If you have a specific domain (yours, a client's, or a bounty target) and want a complete, correlated attack-surface report without writing your own queries or stitching results together yourself, that's what NullBlocks is built for.
Plenty of consultants and hunters use both — Censys for broad discovery, NullBlocks for the deep, correlated pass on a specific target.
Try a free NullBlocks report →