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Global probes
Confirm connectivity from a neutral network to rule out local firewall rules or ISP filtering.
Free Online Tool
Port Checker
Port Checker is the dedicated port checker for SRE, DevOps, and security engineers to validate connectivity, share common port checker knowledge, and respond to outages faster. This port checker keeps your investigations focused on the exact services that matter.
Free online port checker
LIVEEnter an IP address or hostname with a target port to verify connectivity from our cloud-based port checker probe.
Always confirm you have permission before scanning or testing endpoints you do not own.
Instant port testing
Engineered for the Port Checker workflow
Modern operators need fast answers. Port Checker combines live port checker testing, best practices, and documentation in one place so the port checker workflow stays consistent for every team member.
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Actionable guides
Each featured port includes setup checklists, troubleshooting flows, and security reminders.
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Operations ready
Crafted for on-call teams with responsive design, dark mode, and multilingual support.
Instant port testing
Popular ports at a glance
Jump straight into the guides for the ports Port Checker users ask about most often, then run a port checker against each service to confirm availability.
Port
HTTPS 443
Encrypt web applications with TLS certificates on port 443.
Port
SFTP
Transfer files securely through SSH tunnels.
Port
SSH
Manage servers remotely with encrypted shell access.
Port
SMB 445
Serve file shares and authentication over TCP.
Port
SMB over TCP
Serve file shares and authentication over TCP.
Port
HTTP 80
Serve web traffic without encryption on port 80.
Port
DNS 53
Provide name resolution for infrastructure.
Port
Port 22
Manage servers remotely with encrypted shell access.
Port
Telnet
Legacy plaintext remote console access.
Port
DNS Services
Provide name resolution for infrastructure.
Port
SNMP
Monitor infrastructure with SNMP polling and traps.
Port
Samba
Serve file shares and authentication over TCP.
Port
RDP
Provide Windows remote desktop access.
Port
NTP
Distribute precise time to fleet devices.
Port
ICMP
Test reachability and latency with ICMP echo.
Port
FRP
Expose internal apps through reverse tunnels.
Port
Minecraft Server
Host multiplayer Minecraft worlds.
Port
Port 3389
Provide Windows remote desktop access.
Port
FTP
Serve classic file transfers on ports 20/21.
Port
IMAP 143
Retrieve email messages from servers.
Port
SQL Services
Expose relational databases to applications.
FAQ
Frequently asked questions
Get clarity on how port forwarding works, how to interpret Port Checker results, and why some ISPs block certain ports.
What is port forwarding?
Port forwarding maps an external port on your router or firewall to an internal service. It enables access from the internet to devices on private networks.
Why do ISPs block common ports?
Consumer ISPs often block ports such as 25, 80, or 445 to limit malware and spam. Contact your provider about business plans if you need them opened.
How often should I recheck ports?
Verify ports after network changes, firewall updates, or security incidents. Automate recurring checks for mission-critical services.
Why do I see "closed" or "filtered" when my service is online?
External checks can be blocked by firewalls, cloud security groups, ISP filtering, geo rules, or source-IP allowlists. Verify the full path from the internet to your service and compare with an internal test.
What do open, closed, and filtered mean?
Open means the target accepted a connection on that port. Closed means the host was reachable but that port was not accepting connections. Filtered means packets were blocked or dropped by a firewall or ACL, so the exact state cannot be confirmed.
Do you store scan results or my targets?
We process the host and port you submit to run checks and keep limited technical logs for reliability and abuse prevention. See the Privacy Policy for details on retention and handling.
Does this replace production monitoring?
No. This tool is best for point-in-time diagnostics. For production systems, pair it with continuous monitoring, service health metrics, and alerting.