If you’re setting up Winlink, you’ll need to pick a modem to actually move your messages over the air, and the two real options are ARDOP and VARA. They solve the same problem in different ways, and the right choice depends more on your priorities than on either being objectively better.
ARDOP: open source, built for Winlink specifically
ARDOP (Amateur Radio Digital Open Protocol) was developed specifically for Winlink and released as fully open-source software, with no licensing fees or closed-source components anywhere in the chain. That openness matters to some operators on principle, and it also means ARDOP will keep working exactly as documented without depending on a single developer’s continued support the way a closed commercial product might.
VARA: closed source, generally faster
VARA takes the opposite approach: closed source, developed and maintained by a single author, with a free tier and a paid tier that unlocks higher data rates. In most real-world comparisons, VARA outperforms ARDOP in throughput and connection reliability, particularly on HF, which is exactly why VARA has become the default recommendation for new Winlink users despite not being open source.
Which one should you actually run
For most people building a practical Winlink station, I’d start with VARA on the free tier and only step up to a paid license if you’re regularly hitting its limits. Keep ARDOP as a backup option in your Winlink Express configuration, since having a second working modem costs nothing and means you’re not dead in the water if a VARA-specific issue ever crops up. Redundancy is cheap here, so there’s little reason not to have both configured even if you have a clear favorite.
Related reading: What Is VARA? · VarAC · Pat Winlink Client