My IP Check
Your public IP address and network location, detected automatically.
Loads automatically when you open NetChecks — no input needed. Use the Refresh button to re-check after switching networks or reconnecting your VPN.
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All-in-One Scan
Runs every relevant check against one IP or hostname in a single pass: DNS, whois, ping, traceroute, a well-known-ports scan (1-1024), HTTP headers and the SSL certificate.
Enter a domain or IP address and run it to check DNS, whois, ping, traceroute, common ports, HTTP headers, and the SSL certificate all at once.
Most checks run in parallel - typically finishes in about 30 seconds, longer if the target is slow or unreachable.
The port scan step only runs once the consent checkbox above is checked - every other check runs regardless.
Ping
Send ICMP echo requests to a host to check reachability and latency.
Enter a hostname or IP address and press Ping to send ICMP echo requests and measure round-trip latency.
Traceroute
Trace the network path (hop by hop) to a destination host.
Enter a hostname or IP address and run it to see every network hop between this server and the destination, with latency per hop.
DNS Lookup (Nslookup)
Query DNS records: A, AAAA, MX, TXT, NS, CNAME, SOA, PTR, SRV, CAA.
Enter a domain, choose a record type (A, AAAA, MX, TXT, NS, CNAME, SOA, PTR, SRV, or CAA), then look it up.
Whois
Look up registration information for a domain or IP address.
Enter a domain or IP address to look up its registration details — registrar, owner organization, and important dates.
Blacklist Check
Check whether an IP address or domain is listed on public spam/abuse blocklists (DNSBL).
Enter an IPv4 address or domain and run it to check 7 public DNSBL/RBL blocklists at once - each shows as listed, not listed, or check failed.
TCP Port Scan
Check whether TCP ports are open on a host or IP: common ports, a custom list, or the full 1-65535 range.
Enter a host or IP, pick common ports, a custom list, or the full range, then scan to see which TCP ports respond.
A full range scan can take up to ~100 seconds. Large scans (more than 100 ports, including custom ranges/lists) are limited to 1 per minute per visitor.
Open ports (0)
Learn more about TCP Port Scan
What it is
Port Scan tests the state of a set of TCP ports on a given target, revealing exactly which network services are reachable from the outside at a given moment - basic information for any security audit or network configuration validation.
How it works
For each port tested, the tool attempts a standard TCP connection via a SYN handshake. Three outcomes are possible from that attempt: the port responds and accepts the connection (it is open, a service is actively listening there), it responds but explicitly rejects the connection (it is closed, the host is reachable but nothing is listening at that specific spot), or no response arrives within the allotted time (it is filtered, which usually reflects a firewall silently dropping the request without ever letting it reach the service or even respond to it).
Reading the results
An open port is neither good nor bad news in itself - it is entirely the context that determines whether it is expected or a problem: port 443 open on a public web server is perfectly normal and desired, that same port open on an internal workstation with no reason to expose a web service is on the other hand suspicious and worth investigating. A filtered port (no response at all) rather than a closed one (an explicit rejection) is often a sign that a firewall is intercepting the request upstream of the server itself, before it even reaches it - a useful distinction for knowing where to look when a block is unexpected.
Common mistakes
A common confusion is treating a filtered port as equivalent to a closed one in an audit report, when the distinction is operationally important: a closed port proves the host is reachable and nothing is listening, while a filtered port proves nothing about what is actually behind the firewall - the service could well be running normally, simply protected. Another trap: a port scan run from one point on the network only reflects visibility from that exact point - a port can appear closed from the internet but perfectly open and reachable from the internal network, which is often the intended configuration rather than an anomaly.
When to use it
Auditing a server's real network exposure before it goes into production, to make sure no unintended service is listening publicly. Concretely confirming that a firewall rule actually blocks the intended port once applied, rather than relying solely on the declared configuration. Confirming that a service is genuinely reachable from the outside after a deployment or a NAT rule change, before announcing its availability. Quickly checking, as part of a routine check, that no unexpected port was left open by mistake after a technical intervention.
HTTP Header Inspector
Fetch the HTTP response status and headers for a URL.
Enter a URL to fetch its HTTP response status code and every response header the server sends back.
SSL / TLS Certificate Checker
Inspect a host's TLS certificate: issuer, validity dates, and days remaining.
Enter a hostname to inspect its TLS certificate — issuer, validity dates, and days remaining before it expires.
Geo-IP Lookup
Look up the geographic location and network info for an IP address. Leave empty to look up your own public IP.
Enter any IP address, or leave it empty to look up your own, to see its approximate location and network/ISP info.
Subnet / CIDR Calculator
Computed entirely in your browser — no data sent to the server.
Enter an IP address and CIDR prefix (e.g. 192.168.1.0/24) to instantly compute the network range, broadcast address, and usable host count.
Speed Test
Basic download/upload throughput test against this server (accuracy depends on the server's own uplink).
Press Start to measure download and upload throughput against this server. Accuracy depends on this server's own connection.
Country Code Dictionary
ISO 3166-1 alpha-2 country codes — searched entirely in your browser.
Search or browse the list of ISO 3166-1 alpha-2 country codes, looked up entirely in your browser.
| Country | ISO Code |
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Phone Dialing Code Dictionary
International calling codes by country — searched entirely in your browser.
Search or browse international calling codes by country, looked up entirely in your browser.
| Country | Dial Code |
|---|
World Clock
Pick a time zone to see the current time — drag the globe to spin it.
Pick a time zone from the list, or drag the globe, to see the current time there.
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Drag to rotate the globe.
French Mobile Network Status
Mobile antenna sites down or under maintenance in France, by operator (Orange, Free, SFR, Bouygues Telecom), from ARCEP's public data. Snapshot updated once a day by ARCEP - not a minute-by-minute feed.
Browse mobile antenna and fibre outage data by French operator — no input needed, updated automatically from ARCEP's public data.
Most affected departments
Number of sites currently down or under maintenance, by department. Click an operator above to filter.
Data: Arcep — Sites indisponibles · Official network status map
Fixed Network (Fibre)
Fibre (FTTH) network quality by operator: reported-outage rate and connection-failure rate, from ARCEP's public data. Monthly indicators, 6-month rolling average - not a live feed like the mobile section.
By operator (parent group)
Averages over the last 6 available months, per infrastructure-operator parent group.