flrig is a free, open-source transceiver control application for macOS (and other platforms) that gives amateur radio operators direct, software-driven command over their radio hardware — frequency, mode, power, and more — from a single persistent window on the desktop.
What is flrig?
flrig is a dedicated rig-control front-end for ham radio transceivers, built to work as a standalone controller or as a back-end CAT (Computer Aided Transceiver) server that feeds frequency and mode data to companion logging and digital-mode applications like fldigi. It speaks the native command dialects of hundreds of radios — from Icom and Yaesu to Kenwood, Elecraft, and beyond — over serial or USB-serial connections.
The project is maintained by W1HKJ (Dave Freese) and the fldigi development team, the same group behind fldigi, flmsg, and flamp. That pedigree matters: flrig has been hammered on by serious HF operators for years, and the serial-timing quirks that used to derail rig-control software have largely been ironed out.
What does flrig do best?
flrig excels as a transparent bridge between your Mac and your transceiver — set it running once and forget it. Every other piece of ham software (fldigi, WSJT-X via Hamlib, JS8Call, and others) can query flrig's XML-RPC server for the current VFO frequency and mode, so your entire station software stack stays in lock-step without each app fighting over the serial port.
- Real-time VFO display — large, readable frequency readout that mirrors the rig's actual front-panel state, not just what the software last sent.
- Mode and filter control — switch between SSB, CW, AM, FM, and digital modes without touching the radio.
- Power and attenuator sliders — useful when running digital modes where you want precise, repeatable output levels.
- Band-stacking memory — quickly jump between bands without re-tuning by hand.
- Dual-VFO support — for rigs that expose both VFOs, flrig lets you monitor and switch between them in software.
Where it really shines is in digital-mode operating. Running FT8 in WSJT-X while simultaneously logging with a third app? flrig serialises all CAT traffic through a single connection, eliminating the port-conflict errors that used to crash sessions mid-contest.
Is flrig free?
Yes — flrig is completely free, open-source software released under the GNU General Public License. There is no paid tier, no feature unlock, and no account required. You can download it directly from the official site at w1hkj.org, or install it on macOS via Homebrew Cask with a single command.
Who should use flrig?
flrig is aimed squarely at licensed amateur radio operators who run a computer-connected transceiver. If you operate digital modes (FT8, PSK31, RTTY, Olivia), participate in contests where logging software needs to know your frequency automatically, or simply want to control your rig from the keyboard while your hands are on the keyer, flrig fills that gap cleanly.
It is not a beginner app in the sense that setup requires knowing your rig's CAT baud rate, stop bits, and CI-V address (for Icom radios). The documentation at w1hkj.org is thorough, but you will need to spend 20–30 minutes with it and your radio's manual before everything clicks. Once it does, though, the configuration rarely needs touching again.
Casual SWL listeners, podcast producers, or anyone using a Mac purely for audio work will find nothing here for them — this is specialist operator software. The closest thing in the non-ham world would be something like MIDI Device Explorer or a DAW's external hardware controller panel, but for a very different hardware ecosystem.
How does flrig compare to alternatives?
The main alternative for rig control on macOS is Hamlib (the library, exposed through rigctld), which many apps use directly. Hamlib is powerful and has broader third-party support, but running rigctld manually in a Terminal window and keeping it stable across macOS updates is more friction than flrig's point-and-click setup. MacLoggerDX bundles its own rig control but locks it inside a paid logging application — useful if you want an all-in-one, less so if you prefer mixing tools. RUM Log similarly combines logging and control. flrig sits in a different category: it does one job (rig control) and does it well, with a documented XML-RPC API that any developer can target.
For operators already in the fldigi ecosystem, flrig is effectively the expected companion; using anything else creates unnecessary integration work.
What are the main limitations of flrig?
The UI is functional rather than beautiful — it was clearly designed by engineers for engineers, and it shows. On a Retina display the controls look dated compared to modern macOS apps. There is also no AppleScript or Shortcuts integration, so automation beyond what the XML-RPC server exposes requires custom scripting. Finally, Bluetooth serial adapters can introduce timing jitter that confuses some rigs; a wired USB-serial adapter is strongly recommended.
