Wi-Fi analysis · site surveys · network tools

See your Wi-Fi the way your users feel it.

Fresnel scans the air, maps signal on your floor plans and tests the network from the spot you stand on. A native desktop app for Linux and Windows. No account, no cloud, no internet needed.

Download How it works

Free and open source (MIT) · Linux & Windows

Survey · Ground floor · Signal

−50 −60 −67 −75 dBm

Illustration

Real dBm

Read from the driver (nl80211 on Linux, Native Wifi on Windows). Percent is never passed off as dBm.

Fresh samples only

A survey point stores only what a new scan heard there, never the cache from a minute ago.

Unknown stays unknown

What the hardware doesn't report is left empty. Estimates are labelled as estimates.

Offline, local

Projects live in a local database. Nothing leaves the computer unless you send it.

What you can do with it

From a quick look at the channels to a full survey report for a customer.

Live scan

Every access point in range: SSID, BSSID, signal in dBm, channel and width, band, PHY (Wi-Fi 4–7), security and BSS load. Plus your own connection with its TX/RX rates.

Channel overlap map

See who shares your channel on 2.4, 5 and 6 GHz, how wide each network is, and where there's room to move.

Site surveys

Projects, buildings and floors. Import a floor plan (PNG, JPEG, SVG), set the scale with two clicks, then walk and press Measure Here.

Heatmaps

Signal per network or per AP, coverage against a target, AP overlap, which AP serves each spot, and pass/fail against your requirements.

Access points on the plan

Mark where each AP hangs and link the BSSIDs it broadcasts. Fresnel suggests the radios heard strongest at that spot.

Requirements

Profiles such as “Office data” or “Voice / video” turn readings into pass or fail per point and per floor, with the reason for each failure.

Rogue & evil-twin detection

Flags transmitters using your SSIDs that aren't your access points, and copies of your network with weaker security.

Notes & photos

Attach notes and photos to points, APs and pins on the plan (“metal cabinet”, “4 m ceiling”). Location data is stripped from report copies.

Survey reports

One click from a surveyed floor to a report with heatmaps, findings, tests and photos, ready to print to A4 PDF. Data also exports as CSV and JSON.

How a survey works

Five steps from an empty floor plan to a report.

1

Install and scan

Pick your Wi-Fi adapter. The Live page shows every network around you straight away; no admin rights needed.
2

Import the floor plan

Drop in a PNG, JPEG or SVG and draw one line of known length, so distances are in metres.
3

Walk and measure

Stand somewhere, click that spot on the plan, press Measure Here. Optionally run ping and iperf3 from the same spot.
4

Read the heatmaps

Signal, coverage, overlap and serving AP, interpolated between your points. Weak spots and pass/fail show up at once.
5

Export the report

Add your logo and company name, pick the networks, and print to PDF for the customer or your records.

Network tools, built in

When the signal is fine but the network isn't. Every tool shows its results live and keeps a history.

Ping A set count or until stopped, with a live latency chart, loss and jitter.
Traceroute / MTR Loss and latency per hop, hop names, continuously if you like.
DNS lookup Ten record types, your DNS or any server, up to five side by side.
Port check Is it open, closed or filtered? Presets for common services.
iperf3 TCP throughput to your own iperf3 server, upload and download, second by second.

Run over the system's normal route, or tied to one Wi-Fi adapter; Fresnel then refuses rather than quietly testing over Ethernet or a VPN. Every result shows which interface it used. No admin rights. Nothing is contacted unless you type it.

Tools · Traceroute

Hop	Host	Loss	Avg	Best	Worst
1	gateway.lan	0 %	2.4 ms	1.9 ms	4.1 ms
2	10.20.36.3	0 %	4.6 ms	3.8 ms	7.0 ms
3	core1.isp.example	0 %	5.1 ms	4.4 ms	6.2 ms
4	no answer	100 %	—	—	—
5	edge.cdn.example	0 %	9.8 ms	8.7 ms	12.3 ms

Illustration

Download

Builds from the latest release on GitHub.

Windows

Windows 10 and 11 · 64-bit installer

Download .exe

Installs for your user only; no admin rights.
Works without internet (includes WebView2).
Not code-signed yet: SmartScreen may warn on first run (“More info” → “Run anyway”).
To list access points, Windows needs Location turned on, including for desktop apps.

Linux (.deb)

Ubuntu, Debian and derivatives · x86-64

Download .deb

Install: sudo apt install ./Fresnel_*_amd64.deb
Needs NetworkManager (the default on desktop Ubuntu and Fedora).
No root needed to run.

Linux (AppImage)

Other distributions · x86-64

Download AppImage

chmod +x Fresnel_*.AppImage and run it.
Ubuntu 24.04 without libfuse2: add --appimage-extract-and-run.
Needs NetworkManager.

SHA256SUMS · All releases · Source code

Questions

Does Fresnel need the internet or an account?

No. Everything runs and is stored on your computer. The only things it contacts are hosts you type into a tool, such as an iperf3 server or a DNS server.

Do I need admin or root rights?

No. Scanning, surveys and all the tools work as a normal user. On Linux, ping uses unprivileged ICMP sockets; if your system disallows them, Fresnel times TCP connections instead and says so.

Which Wi-Fi adapters work?

Any adapter your system's Wi-Fi service can use. On Linux the driver should support nl80211 for real dBm (most do); otherwise signal is shown as a percentage and labelled that way.

How accurate are the heatmaps?

They interpolate between the points you measured and don't model walls, so measure on both sides of walls that matter. Shading stops 3 m from the nearest point instead of guessing further.

Is it free?

Yes. Fresnel is open source under the MIT license.