Network tools — Free Online Network Tools
DNS, SSL, ports, headers, IP and subnet utilities for diagnosing your own servers and networks. Use them only on systems you own or have permission to test.
Network diagnostics — DNS, SSL, ports, headers, IP, subnets — for engineers who need to troubleshoot their own servers. These tools run on our server because they fundamentally need to make outbound network requests; we never store the targets you query.
Compare Network tools — Free Online Network Tools
| Tool | Input | Output | Max size | Runs in browser? |
|---|
| Open Port Checker | URL, IP or domain | Diagnostic data | 50 MB | No (server) |
| Port Range Checker | URL, IP or domain | Diagnostic data | 50 MB | No (server) |
| DNS Lookup | URL, IP or domain | Diagnostic data | 50 MB | No (server) |
| DNS Propagation Checker | URL, IP or domain | Diagnostic data | 50 MB | No (server) |
| Reverse DNS (PTR) Lookup | URL, IP or domain | Diagnostic data | 50 MB | No (server) |
| IP Address Lookup | URL, IP or domain | Diagnostic data | 50 MB | No (server) |
| HTTP Headers Viewer | URL, IP or domain | Diagnostic data | 50 MB | No (server) |
| HTTP Status Checker | URL, IP or domain | Diagnostic data | 50 MB | No (server) |
| SSL Certificate Checker | URL, IP or domain | Diagnostic data | 50 MB | No (server) |
| CIDR Calculator | URL, IP or domain | Diagnostic data | — | Yes |
| IPv4 Subnet Calculator | URL, IP or domain | Diagnostic data | — | Yes |
| What Is My User-Agent | URL, IP or domain | Diagnostic data | — | Yes |
| Traceroute (HTTP path) | URL, IP or domain | Diagnostic data | — | Yes |
| Ping & Latency Test | URL, IP or domain | Diagnostic data | — | Yes |
| WHOIS Lookup (Domain) | URL, IP or domain | Diagnostic data | 50 MB | No (server) |
| MX Record Lookup | URL, IP or domain | Diagnostic data | 50 MB | No (server) |
| SPF, DKIM & DMARC Checker | URL, IP or domain | Diagnostic data | 50 MB | No (server) |
| MAC Address Vendor Lookup | URL, IP or domain | Diagnostic data | — | Yes |
| HTTP Redirect Chain Checker | URL, IP or domain | Diagnostic data | 50 MB | No (server) |
Frequently asked questions
- Are the network tools free?
- Yes — every network diagnostic here is free, no signup, no daily limit beyond a per-IP rate limit to keep the API fair for everyone.
- Do you log the domains and IPs I check?
- We log per-request stats (status code, duration) for operational metrics, but the targets themselves are not stored or shared. We never sell logs.
- Why do these tools run on a server, not in my browser?
- Browsers can't open arbitrary TCP sockets, run DNS queries, or read SSL certificates from third-party hosts — those operations are blocked for security. We proxy them via our API server, in-memory only.
- Can I check internal / private IPs?
- No — for safety, we refuse to query private (RFC1918) ranges, link-local IPs, or localhost. Use the tools only against systems you own or have permission to test.
- Is there a rate limit?
- Yes — a small per-IP budget (typically 60 requests per minute) keeps the API responsive for everyone. Email us if your team needs a higher limit.