6 Online Port Scanners to Find Opened Ports on Server and IP

Keeping track of open ports on your servers and network is a critical step in securing your infrastructure against cyber threats. Unmonitored open ports are like unlocked doors just waiting for attackers to enter. Thankfully, you‘re not defenseless in this situation. There are many powerful online port scanners available to help identify vulnerabilities so you can lock down your systems.

In this comprehensive guide, we‘ll explore six top options among the many online port scanners available today. I‘ll share my insights as an IT security analyst on the pros and cons of each scanner along with recommendations based on different use cases. My goal is to help you, as a fellow tech geek, understand how to choose the right port scanning solution for your needs. Let‘s dive in!

A Quick Refresher on Port Scanning

But first, let‘s refresh on some key concepts for anyone new to port scanning. Think of a port as an open doorway that allows external connections to services running on a server. By scanning ports, we‘re essentially knocking on doors to see which ones open up.

Here are some important facts to know:

There are 65,535 TCP and UDP ports available per network interface. Scanning probes each to check the status.
Open ports indicate services or applications listening for connections on that port.
Identifying open ports is critical for security audits to find weaknesses.
Malicious port scans probe networks for vulnerabilities and can trigger intrusion alerts.
Only scan systems you own or have clear permission for to avoid legal issues.

Now that we‘re caught up on port scanning basics, let‘s explore some of my top online scanner recommendations!

1. Nmap Online Port Scanner – Powerful and Feature-Rich

Nmap is arguably the most reputable port scanner used by security pros today. This free open source tool offers advanced functionality like OS detection, scripting, and detailed reporting.

The Nmap Online scanner makes Nmap‘s capabilities accessible through any web browser. Under the hood, it utilizes Nmap‘s powerful scanning engine to probe ports.

Here are some key advantages:

Supports TCP connect, SYN, and ACK scans to accurately map open ports.
Customizable port range and scanning intensity for flexibility.
Banner grabbing fingerprints services like Apache/Nginx to recognize.
Free tier permits scanning a single IP with top 100 common ports.
Paid plans enable larger scan ranges and additional Nmap features.

In my experience, this is one of the most fully-featured online port scanners available today. The convenience of the web interface combined with Nmap‘s scanning strengths make this a top choice.

If you‘re willing to install local software, the native Nmap application offers the full breadth of features. But the online version is great for basic vulnerability checks from any device.

2. Geekflare Port Scanner API – Ideal for Custom Tools

APIs unlock interesting possibilities for integrating port scanning into your own tools and apps. Geekflare‘s Port Scanner API delivers scanning functionality through a straightforward API.

Here are some benefits I like about their API:

Simple API enables port scans using HTTP requests without software.
Supports TCP connect, SYN, and UDP scan types.
Scan single IPs or ranges of up to 65536 ports.
Clean JSON output formats results nicely.
500 free scans daily. Affordable paid tiers for more capacity.

For developers, this API makes it easy to build custom admin dashboards, security monitors, and more with port scanning capabilities baked in.

The generous free tier is nice for smaller workloads. If building commercial apps, the low-cost paid plans scale up nicely.

Overall, I think this is a leading API option for programmatic port scanning today.

3. YouGetSignal – Simple Web Scanner

YouGetSignal is a straightforward online port scanner with an intuitive interface. It‘s less fully-featured than Nmap but handy for basic vulnerability checks.

You enter a target IP address and select port lists to scan:

Top 10 Common Ports – Hits services like HTTP(S), FTP, SMTP.
Top 50 Ports – Adds Telnet, SMB, MySQL and more.
All Ports – Scans the full 1-65535 range.

This tool is free to use without registration required. Just note it only allows one IP per scan. The simple interface makes it easy to perform a few quick scans. But it lacks more advanced options of commercial solutions.

4. Pingcastle – Scanner for Internal Networks

Pingcastle offers another free online port scanner with a bonus feature – it can scan your internal network if you have a VPN connection.

You can define a custom port range and timeout per port. It reports back open ports and identified services. A handy "Compare" function lets you contrast scans before and after a config change.

The limitation is that it only allows one scan at a time. This works fine for occasional spot checks but lacks automation for large-scale monitoring.

One neat capability is the option to scan an internal IP over an active VPN connection, broadening its use cases.

5. Hackertarget – Leverages Advanced Nmap Scans

Hackertarget is a collection of online security tools with scanning powered by Nmap. It supports:

TCP connect, SYN, and UDP scans.
Customizable port and host timeouts.
Banner grabbing for identifying services.
Up to 20 ports free. More with subscription plans.

The output even includes the raw Nmap XML results for detailed analysis.

This is another excellent option if you want Nmap scan types and configuration minus the software installation. Features like OS detection need a subscription. But the free scans still offer a lot of value.

6. Netcraft – Basic Port Scans

Netcraft offers a free and simple online port scanner. It lets you enter a target and select TCP or UDP scan types along with common port groups:

General ports like HTTP/HTTPS, FTP, Telnet
Mail ports such as POP3, IMAP, SMTP
Top 10, 50, or 100 most popular ports

Advanced options are limited compared to Nmap. But the tool is handy for quick scans from any device when you just need a basic list of open ports on a few IPs.

Recommendations Based on Use Cases

With many port scanners to choose from, which is the best fit? Here are my recommendations based on common use cases:

For occasional spot checks: YouGetSignal, Pingcastle, and Netcraft all offer free and straightforward online scanners suitable for quick vulnerability checks on a few IPs at a time.

For large-scale scanning: Nmap Online and Geekflare‘s API scanner have the scalability, speed, and features to automate scans across large IP ranges.

For flexibility from any device: The online scanners provide accessibility from any laptop, mobile device, or even Raspberry Pi with an internet connection. No software to install.

For integrated scanning in tools: Leverage Geekflare‘s or other port scanning APIs to build custom scanning functionality into your own security tools and software.

For advanced features and customization: Utilize the full open-source Nmap locally for hundreds of scan types, detailed reporting, scripting and more – with a learning curve.

Best Practices for Securing Your Ports

Scanning for open ports provides vital visibility. But locking them down is equally important for security:

Close unnecessary ports – Disable unused services to reduce your exposure.
Limit access – Only allow required connections inbound through firewall policies.
Require authentication – Enforce strong logins for management protocols like SSH and RDP.
Scan frequently – Automate scans of critical systems for changes from a known good baseline.
Prioritize risks – Catalog assets and rank priorities based on potential impact if compromised.
Patch aggressively – Maintain up-to-date OS and software to prevent known exploitations.

Port scanning is just one piece of an effective cybersecurity strategy. But it remains a quick and easy first step towards hardening your defenses.

Final Thoughts

I hope mapping out these leading online port scanners helps you find the best match for your needs as a fellow cybersecurity geek. Just remember to gain proper permission before scanning systems and use this visibility to continually strengthen your security posture.

With some foundational knowledge and these scanner recommendations, you‘re equipped to start discovering and addressing potential weak points before attackers do. Stay vigilant out there as threats evolve! Please reach out if you have any other questions.