XDA published a walk-through of an Ethernet troubleshooting saga that ended with the writer realising the RJ45 crimp was the culprit, not the router. The fix took minutes; the diagnosis had taken hours. It’s a familiar loop for anyone who has ever chased “why is this connection slow” through the wrong layer. A LAN diagnostic app that reports actual link speed, packet loss per hop, and throughput to a real endpoint would have surfaced the physical-layer problem in the first ten minutes.
We tested seven of the best apps for LAN and network diagnostics on Windows, macOS, and Linux desktop. The picks span packet inspection, throughput testing, path monitoring, LAN discovery, and Wi-Fi survey work — the categories that cover most home and small-office network problems before you call the ISP.
What to look for in a LAN diagnostic app
- Real throughput measurement. A speed test to a public server measures your ISP link, not your LAN. Tools that push traffic between two of your own machines are what tell you if the wired link is negotiating at 1 Gbps or falling back to 100 Mbps.
- Hop-level visibility. Traceroute plus ping stats per hop shows where the latency actually happens. The problem is rarely at the destination.
- Packet-layer inspection. When the transport is behaving badly, you need to see the frames. Wireshark-class tools have been the answer for two decades.
- Local run, no telemetry. A network diagnostic app that sends your topology to a cloud dashboard is fine for managed services; for private LAN work you want on-device.
- Cross-platform consistency. Home labs mix Windows, macOS, and Linux boxes. Tools that ship on all three save you setup time.
- Free floor. Half of these should be free. If the paid tier is worth it, the free tier should still be usable.
Quick comparison
| App | Best for | Platforms | Free plan | Starting price/mo |
|---|---|---|---|---|
| Wireshark | Packet inspection, protocol analysis | Windows, macOS, Linux | Yes, fully | Free |
| iPerf3 | Point-to-point throughput on your LAN | Windows, macOS, Linux | Yes, fully | Free |
| PingPlotter | Visual latency and packet loss over time | Windows, macOS | Yes, limited | $6 for Standard |
| WinMTR | Traceroute with per-hop ping stats | Windows | Yes, fully | Free |
| LAN Speed Test | Quick LAN throughput to a file share | Windows, macOS | Yes, limited | $10 one-time for Pro |
| Angry IP Scanner | Fast LAN device discovery and port scan | Windows, macOS, Linux | Yes, fully | Free |
| NetSpot | Wi-Fi survey and interference mapping | Windows, macOS | Yes, limited | $50 one-time for Home |
The apps
1. Wireshark — Best for packet inspection
Wireshark is the gold standard packet analyzer, and no other tool in the category comes close for the price of zero. Capture on any interface, filter with a syntax that reads like plain English (tcp.port == 443 and ip.dst == 10.0.0.5), and follow a conversation through TCP handshakes, retransmissions, and resets. When “the connection is slow” turns out to be aggressive Duplicate ACK storms, Wireshark shows you within a minute.
Where it falls short. The learning curve is real. If you don’t know what a SYN retransmission means, the capture reads as noise. Wireshark also captures everything, so on busy links you fill the buffer fast unless you filter early.
Pricing.
- Free: fully, open-source, no paid tier.
- Paid: none.
Platforms: Windows, macOS, Linux.
Download: Wireshark
Bottom line. Pick Wireshark for any diagnosis that reaches the packet layer. It’s the tool a network engineer would open first.
2. iPerf3 — Best for point-to-point throughput
iPerf3 is the cross-platform utility that answers the one question every LAN diagnosis needs: what is the actual bandwidth between two hosts on my network? Run it in server mode on one machine, client mode on another, watch the reported throughput. If the number is 94 Mbps on a gigabit link, you have a physical-layer problem. That’s the exact scenario the XDA writer chased for hours. TCP and UDP tests, tunable window sizes, and JSON output make it scriptable.
Where it falls short. iPerf3 is command-line only. Some third-party GUI wrappers exist, but the standard experience is a terminal. Firewalls need to be configured to let the test port through.
Pricing.
- Free: fully, open-source.
- Paid: none.
Platforms: Windows, macOS, Linux.
Download: iPerf
Bottom line. If you have never run iPerf3 between two of your own machines, do it now. It’s the fastest way to confirm your LAN is doing what you paid for.
3. PingPlotter — Best for visual latency monitoring
PingPlotter turns “the internet is slow” into a graph you can send to your ISP. Continuous traceroute plus ping to a target, per-hop packet loss over time, and a session log that survives long enough to prove a pattern. The 2026 release added an inline anomaly detector that highlights when a hop crosses a threshold, which cuts hours off a call-your-provider argument.
Where it falls short. Windows and macOS only. There is no Linux client. The free tier caps concurrent sessions to a small number, which is fine for one or two links but not for a whole home lab.
Pricing.
- Free: one target session, limited history.
- Paid: $6 per month for Standard, $16 for Professional with unlimited targets.
Platforms: Windows, macOS.
Download: PingPlotter
Bottom line. Pick PingPlotter when the problem is intermittent and you need a chart, not a snapshot.
4. WinMTR — Best free traceroute for Windows
WinMTR is a Windows port of the classic MTR tool that combines traceroute and ping into one continuous view. Watch packet loss per hop as it happens, spot the hop that starts dropping packets, and export the report as text. It’s the fastest way on Windows to answer “which hop is bad” without paying for PingPlotter.
Where it falls short. Windows only. Mac and Linux users run the original MTR from a package manager instead. The UI is dated, and there’s no long-term trending or session log. It’s a real-time inspector, not a monitor.
Pricing.
- Free: fully, open-source.
- Paid: none.
Platforms: Windows. (MTR itself runs on macOS and Linux.)
Download: WinMTR
Bottom line. Pick WinMTR when you need a quick answer on Windows and PingPlotter feels like overkill.
5. LAN Speed Test — Best for one-click LAN throughput
LAN Speed Test by Totusoft is the pick when you want a drag-and-drop throughput number without touching the command line. Point it at a file share, choose a test size, watch the read and write speeds report. It’s the fastest way to check a NAS link, a switch port, or a new Wi-Fi 7 setup against your gigabit or 2.5-gigabit expectations. The Pro version adds Server mode so you can test between two machines without a share.
Where it falls short. Windows and macOS only. The free tier caps some features and shows an unlock prompt periodically. Reported numbers depend heavily on the target’s disk speed unless you use Server mode.
Pricing.
- Free: basic tests with a feature nag.
- Paid: $10 one-time for Pro, unlocks Server mode and CSV export.
Platforms: Windows, macOS.
Download: LAN Speed Test
Bottom line. Pick LAN Speed Test when you want a quick confirmation that your NAS or switch link is doing what it should.
6. Angry IP Scanner — Best for LAN discovery
Angry IP Scanner is the open-source utility for finding what’s actually on your network. Scan a subnet in seconds, discover hostnames, MAC vendors, and open ports on every responding device. It’s the first tool to reach for when a new device you can’t identify has joined the LAN, or when you’re mapping the network before diagnosing routing problems.
Where it falls short. The interface has not aged well, and the Java runtime dependency on some platforms can trip up first-time users. It’s a scanner, not a monitor. It takes a snapshot, then stops.
Pricing.
- Free: fully, open-source.
- Paid: none.
Platforms: Windows, macOS, Linux.
Download: Angry IP Scanner
Bottom line. Pick Angry IP Scanner as the first step of any home-lab audit. It’s the cheapest way to confirm the network topology you think you have.
7. NetSpot — Best for Wi-Fi survey
NetSpot covers the wireless half of the diagnostic surface. Site survey mode plots signal strength across a floor plan, discover mode lists every access point and their channels, and inspection mode reports SNR and noise. When the “slow LAN” is actually a congested 5 GHz channel, NetSpot shows it in one screen.
Where it falls short. The free tier is limited to a small number of survey zones, and the Home license is a $50 one-time upgrade before the Pro workflows unlock. Windows and macOS only.
Pricing.
- Free: basic scan and discover.
- Paid: $50 one-time for Home, $150 for Pro.
Platforms: Windows, macOS.
Download: NetSpot
Bottom line. Pick NetSpot when the wired story checks out and you need to prove or disprove that Wi-Fi is the actual problem.
How to pick the right one
Start with iPerf3 on any wired diagnosis. If the number is way below the negotiated link speed, the answer is almost always a physical layer or duplex issue, and no other software will find it faster.
Add Wireshark when the throughput is fine but the connection still misbehaves. Retransmissions and out-of-order packets are the fingerprints Wireshark reads best.
Reach for PingPlotter or WinMTR when the problem is intermittent. PingPlotter for the chart, WinMTR for the free quick look on Windows.
Use LAN Speed Test to check a NAS or switch link against expectations without touching the terminal.
Run Angry IP Scanner first if you don’t fully trust the topology you think you have. It’s the cheapest audit in the category.
Bring in NetSpot the moment you suspect Wi-Fi is the bottleneck. Wired diagnostics can’t help with a congested channel.
FAQ
What is the best free network diagnostic tool for Windows?
Wireshark for packet analysis, iPerf3 for throughput, and WinMTR for hop-level path analysis. All three are free and cover the questions that most home-office diagnoses need to answer.
How do I test the actual speed of my LAN cable?
Run iPerf3 in server mode on one machine, client mode on another, both wired to the same switch. Compare the reported bandwidth to the negotiated link speed. A 1 Gbps cable that’s actually negotiating at 100 Mbps is almost always a bad crimp or a damaged pair, which is the exact issue the XDA writer hit.
Can Wireshark run on macOS?
Yes, Wireshark ships native binaries for macOS, Windows, and Linux. It uses libpcap on Unix and Npcap on Windows.
What is a good alternative to PingPlotter?
WinMTR on Windows and MTR on macOS or Linux cover the same real-time path analysis for free. PingPlotter adds visualisation, long-term history, and anomaly detection that the free tools don’t have.
Do I need to buy anything to test my Wi-Fi network?
NetSpot’s free tier is enough to run a basic scan and see which access points are on which channels. The paid tier unlocks site-survey heatmapping, which most homes don’t need but any small office should consider.
What’s the difference between iPerf and speedtest.net?
Speedtest.net measures your ISP link to a public server. iPerf3 measures the link between two hosts on your own network. For LAN diagnostics, iPerf3 is the correct tool — public speed tests will never help you find a bad Ethernet cable.
