Bogon and private IP checker
Some addresses can never legitimately be the source of traffic from the internet. Seeing one in a log usually means a proxy is misconfigured and you are recording your own infrastructure instead of the visitor.
Free, no signup, no daily limit. We do not store what you check here.
The one that matters most
169.254.169.254 is the link-local address where every major cloud serves instance metadata, including credentials. Any feature that fetches a URL a user supplies — a webhook destination, an avatar importer, a preview generator — will be pointed at it eventually. That is server-side request forgery, and refusing link-local and private ranges before the request is made is the cheap half of the fix.
A private address in your access log is a bug in your logging
If your application records 10.x or 172.16.x as the visitor address, it is recording the proxy in front of it rather than the person. Everything keyed on that address then collapses into a single bucket: rate limits become global, geolocation becomes meaningless, and abuse from one visitor throttles everybody. The fix is trusting exactly the proxies that are really there and reading the forwarded address they set.
Questions
Is a private address dangerous?
Not by itself — most of the world sits behind one. It is dangerous as a destination your server can be told to fetch, and it is a symptom when it appears as a source address in a public-facing log.
What about the documentation ranges?
192.0.2.0/24, 198.51.100.0/24 and 203.0.113.0/24 exist for examples and tests. Real traffic from them means somebody copied an example into a configuration file.
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When you need more than a free tool
This page answers what can be determined offline and from public DNS. The API adds live carrier and mailbox verification, a calibrated confidence score, and the full evidence trail behind every verdict.
Credits never expire. Inconclusive verdicts are never billed. Cancel in one call. See pricing or read the docs.