A packet sniffer captures network traffic so you can read what's crossing the wire, and the right one depends on the question you're asking. Capture tools show you what's in a packet, forensic tools help you work out what happened, and monitoring suites tell you whether the network's healthy.
Start with the question, not the tool
People search for one tool and find nine that look alike. They aren't. Roughly half the names here are free, open source capture tools, and the other half are commercial suites where reading packets is one feature among many. Asking which is best makes no sense until you know which of three questions you've got: what's in this traffic, what happened on Tuesday night, or is my network all right at the moment?
Question one: what's in this traffic?
This is sniffing in the plain sense. Wireshark is where most people begin, and it's free and open source in its own words. If you're on a remote server with no desktop, tcpdump does the capture from a command line and comes from the same project as the libpcap capture library. A common habit is to capture on the server and read the file somewhere more comfortable.
Fiddler belongs here with a warning attached. It's a web debugging proxy, so it works at web traffic level and not on raw packets. If you're a developer asking why an API call failed, that's often all you need. If you're chasing a network fault, it won't see what you're looking for.
Question two: what happened during the incident?
Now you're not watching live, you're reconstructing. NetworkMiner is positioned for exactly this kind of forensics work, reading network traffic so you can go through what happened. Zeek takes a different route: it's an open source network monitor, built for defenders by its own description, and you script what it records. Omnipeek's claim is breadth, saying it decodes thousands of protocols, which matters if your incident involves something more unusual than web traffic.
Before you open any of these on a live network, think about what's in the data. NIST's security glossary treats the terms 'sniffer' and 'packet sniffer' together, listing them alongside passive wiretapping. That's the bit a lot of buyers wouldn't guess, and it tells you how seriously to take the tool. Captured traffic can include anything that isn't encrypted, so get written permission before you capture on a network that isn't yours, and treat the capture file as sensitive. The rules vary by country and by employer, so ask whoever's responsible rather than assuming.
Question three: is the network healthy?
Here's where I'll be blunt. PRTG and SolarWinds Network Performance Monitor aren't sniffers in the strict sense. They're monitoring suites, watching health and performance across your systems, and they earn their place because many people searching for a sniffer really want to know why the network's slow. Capsa sits nearer the middle, describing itself as both a network analyser and a packet sniffer for real-time traffic analysis.
If your problem is a pattern over weeks and not a single conversation between two machines, you're shopping for monitoring, and you'd do better to start there. And if a capture keeps showing you lookups you don't understand, our plain guide to what DNS is will help you read them. Likewise, how a VPN works explains why some traffic in your capture will be unreadable, which no sniffer on this list can change.
The nine, in no particular order
| Tool | Question | What it says it does |
|---|---|---|
| Capsa | Watch a network | Analyser and packet sniffer for real-time traffic analysis |
| Fiddler | Capture | Web debugging proxy for web and network traffic |
| NetworkMiner | Investigate | Network forensics analysis tool |
| Omnipeek | Investigate | Protocol analyser, claims to decode thousands of protocols |
| PRTG | Watch a network | All-in-one monitoring across servers, networks, cloud and OT |
| SolarWinds Network Performance Monitor | Watch a network | Self-hosted network health and performance monitoring |
| tcpdump | Capture | Command-line packet capture, with the libpcap library |
| Wireshark | Capture | Free, open source network analysis tool |
| Zeek | Investigate | Scriptable open source network monitor for defenders |
Capsa
Best for: Network teams who want real-time traffic analysis and monitoring; its Enterprise edition is pitched at pinpointing problems as they happen, the vendor says.
Fiddler
Best for: Developers debugging web calls; it captures, mocks and modifies web and network traffic at proxy level, so don't expect raw packets from it.
NetworkMiner
Best for: Forensic work on traffic you've already got, since the vendor positions it for network forensics and its site mentions a free edition.
Omnipeek
Best for: Engineers with unusual protocols to read; the vendor claims it decodes thousands of them.
PRTG
Best for: Admins after all-in-one monitoring across servers, networks, cloud and OT; the vendor offers a free 30-day trial as of Nov 2026.
SolarWinds Network Performance Monitor
Best for: Teams preferring self-hosted monitoring of network health and performance, pitched by the vendor as hybrid IT visibility.
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tcpdump
Best for: Anyone comfortable at a command line, on a server with no desktop; its release notes list Linux, macOS, FreeBSD, NetBSD, OpenBSD, QNX and Solaris 11.
Wireshark
Best for: Most people's first look inside a capture, as a network analysis tool its own site calls free and open source.
Zeek
Best for: Defenders who want to script what gets recorded; the project describes itself as flexible and scriptable.
My advice, depending on your question
If you're curious, learning or debugging one problem, start with the free capture tools and stay there as long as they're answering your question. You won't have spent anything but time, and you'll learn what network traffic looks like, which makes every other tool easier to judge.
If you're responsible for security, you're past single captures. You want something that records and can be searched afterwards, and the forensic group is where to look. Pick based on the skills on your team, since a scriptable monitor is wasted without somebody who'll write the scripts.
If you're the person who gets the call when the network's slow, don't buy a sniffer at all. Get a monitoring suite, use its trial on your own network and keep a free capture tool on hand for the day you need to see the packets. I'd rather you ran two simple tools that you understand than one big one that you don't.
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Packet capture, answered plainly
Is a packet sniffer the same as network monitoring?
No. A sniffer captures and shows you the traffic itself. Monitoring tracks the health and performance of your network over time. Some suites do a bit of both, but they answer different questions.
Can a packet sniffer read everything on a network?
It can only read what reaches the machine it's capturing on, and it can't read the contents of strongly encrypted traffic without the keys. You'll still see plenty of useful detail about who's talking to whom.
Do I need permission to use one?
Treat it as yes unless it's your own network. Capture files can hold sensitive data, and the rules vary by country and employer, so check with whoever's responsible first.
What's the easiest one to start with?
A free, open source capture tool with a graphical interface is the usual starting point, because you can open a capture and browse it without learning command-line options first.
