Port Scanner
See which ports are open on an IP address. Browsers can't open raw sockets, so this runs server-side — here's how it works.
Port scanner
Server-side scanning is on the way. Here's what it will check.
Why this isn't live in your browser: for security, browsers can't open raw TCP/UDP sockets — they're limited to HTTP(S). A genuine port scan needs a server that can connect to each port, so this tool will run on our diagnostic engine, not in the page.
Common ports it will check
- Pending
80 / 443
HTTP / HTTPS · Web traffic
- Pending
22
SSH · Remote shell
- Pending
21
FTP · File transfer
- Pending
25 / 587
SMTP · Outgoing email
- Pending
53
DNS · Name resolution
- Pending
3389
RDP · Remote desktop
- Pending
3306
MySQL · Database
- Pending
8080
HTTP-alt · Proxies / dev servers
What a port scanner does
A port scanner probes an IP address to find which network ports are reachable from the internet. Each open port is a doorway to a service — a web server, a remote-desktop session, a game host — and knowing which doors are open is essential both for getting services working and for keeping the ones you don't want exposed firmly shut.
The reason it can't run inside this page is fundamental, not a missing feature: browsers are sandboxed and cannot open raw network sockets. They speak HTTP(S) and a handful of safe protocols only. Probing arbitrary ports requires opening direct TCP/UDP connections, which only a server or a native app can do — so a real scan must run server-side against your public IP. The interface above previews exactly what our server-side scanner will check.
How to read results (once live)
- Open — a service is listening and reachable from the internet. Intended for things you host; a red flag if you didn't expect it.
- Closed — the port is reachable but nothing is listening. Generally fine.
- Filtered — a firewall is silently dropping the probe. Usually the safest state for ports you don't use.
Frequently asked questions
Why can't a website scan my ports?
Browsers deliberately can't open raw network sockets — they're sandboxed to HTTP(S) and a few safe protocols. Without raw sockets there's no way to probe arbitrary TCP/UDP ports. A real port scan needs a server (or a local app) that can open those connections to your public IP.
What is a port scan actually checking?
It checks which network ports on an IP address are open (accepting connections), closed, or filtered (silently dropped by a firewall). Open ports indicate services that are reachable from the internet — useful for hosting, and important to lock down for security.
Is it legal to scan ports?
Scanning your own IP address is fine and a normal part of securing your network. Scanning systems you don't own or have permission to test can violate acceptable-use policies or laws, so only scan addresses you control.
How do I check my ports today?
On your own machine you can use tools like nmap, or your operating system's built-in netstat to see what's listening locally. To see what's exposed from the outside, you'll want a reputable server-side scanner — which is what we're building into the Doctor.
Check what your browser can test right now
While the scanner is being wired up, our full diagnosis measures the parts of your connection a browser can reach — speed, latency, stability and privacy leaks — with a plain-English verdict.
Run a full diagnosis