HAMSTR is an open-source program that lets people use Nostr, the decentralized social protocol, without an internet connection. It is aimed at emergency response volunteers, residents of remote areas, and anyone who needs censorship-resistant communication when ordinary infrastructure is down. A radio-connected server relays requests between a client that has no internet access and the Nostr relays it wants to reach.
The project is free and released under the GPL-3.0 license. Its backend is modular, so it can switch between radio transports, from legacy packet radio to newer mesh networking, and it supports Lightning payments and zaps over the air. Windows is listed in the documentation alongside Linux, so this page covers Windows use with that caveat. The most recent code update in the repository is dated August 13, 2026, and development is ongoing.
What Is HAMSTR and How Does It Work?
HAMSTR sits between a client device and the Nostr network. On a normal setup, your Nostr app talks directly to relays over the internet. In HAMSTR's design, the client reaches a server over a radio link, and that server handles the internet side by talking to Nostr relays on the client's behalf.
The key idea is that Nostr itself is simple. Messages, called events, are signed by the user's key and sent to relays, which store and pass them along. Because signing happens with the user's own key, the bridging server does not need to be trusted with it. The server only moves messages, which is why the zero-knowledge design matters.
For a user, the experience should feel like reading and posting on any Nostr client. The difference is the path: the request goes over radio, then through a server, then to the relays, and the response returns the same way. Delays are longer than on broadband, so the system suits slower, deliberate exchanges better than real-time chat.
Who Should Consider Off-Grid Nostr?
Ham radio operators are a natural audience. Many already run packet or digital modes, and HAMSTR gives them a way to bring a public social protocol onto the radio side. Operators interested in experimenting with mesh networking will also find the modular transport design a useful testbed.
Emergency planners and community preparedness groups are another group. A neighborhood network that can pass short messages when the internet is down offers a backup channel, and a Nostr-based layer can carry public notices or coordination messages between members who share a radio setup.
Residents of remote properties, researchers working in the field and travelers in areas with little coverage can use the same approach. People who simply want a decentralized social network that does not depend on one company's servers may also be curious, provided they accept that the setup requires more technical effort than a standard app.
Key Concepts: Relays, Zaps and Radio Transports
A Nostr relay is a server that stores and forwards signed messages. Users choose which relays to connect to, and the network works because many relays carry the same content. HAMSTR's server is the component that reaches those relays on behalf of a radio-only client.
A zap is a Lightning payment attached to a Nostr post or profile, used as a tip or a sign of appreciation. NIP-57 defines how zaps are formed so that recipients and clients can read them. When HAMSTR supports zaps over radio, it is carrying that same kind of payment information along a different physical path.
A radio transport is the method used to send data over the air. Packet radio is an older approach that moves data in discrete frames. LoRa is a long-range, low-power modulation often used for sensor networks. Mesh networking lets nodes forward traffic for one another. Each transport trades off range, speed and hardware cost, which is why the modular design matters.
Key features
Offline Lightning payments over radio
Full NIP-57 zap compliance
Zero-knowledge server design
Modular protocol system
Emergency communications
Remote areas without connectivity
Censorship-resistant communication
Resilient mesh networking via Reticulum
Supported coins
The documentation names the Lightning Network and Nostr as the main networks involved. Lightning payments, including zaps, can be carried over the radio link, and the zap format follows NIP-57 so recipients see them in compatible clients. For payments without Lightning, the requirements point to a Cashu ecash wallet, which handles offline transfers on its own.
How to install HAMSTR on Windows
- 1
Get the program from the official source
Download only from the official website or the project's GitHub repository at github.com/LibertyFarmer/hamstr. Check the Releases section for a packaged build. If no packaged Windows build is offered, you can follow the build instructions in the repository, which are meant for developers and should be done with care.
- 2
Verify the file before running it
Compute the SHA-256 checksum of the downloaded file using a tool such as PowerShell's Get-FileHash command, and compare it with the checksum published alongside the release. If a signature is provided instead, verify it with the signing key listed by the project. Do not run a file whose checksum does not match.
- 3
Install and check the Windows setup
Run the installer or extract the package to a folder you control, following the steps in the project documentation. Windows is listed as a supported platform, but compatibility has not been independently verified, so treat the first run as a test and check the repository's issue tracker for known Windows problems before relying on it.
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Prepare the radio side and optional wallet
Choose a radio transport that matches your hardware, such as LoRa or packet equipment, and confirm that your planned use of encryption over amateur radio is allowed where you live. If you want offline payments, set up a Cashu ecash wallet, which the requirements list as an option that does not need Lightning.
System requirements
- Windows is listed among the supported platforms in the project documentation, alongside Linux
- Radio hardware that matches the transport you choose, such as LoRa modules or packet radio equipment
- A Cashu ecash wallet if you want offline payments, since Lightning is not required for that option
How to use HAMSTR
HAMSTR works best when you plan the setup before you need it. The program connects a radio-only client to a server that reaches Nostr relays, so the steps focus on the radio link and the account side. Work through the list below once on a test network before relying on the system in an emergency.
- Choose the radio transport that matches your hardware, such as LoRa or packet radio, and confirm that the modules you need are available in your build.
- Check the rules for your area and your license class before you transmit, especially if you plan to use encryption on amateur bands.
- Start the HAMSTR server on the machine that has internet access and connect it to your radio equipment.
- Set up the client side on the radio-only device and confirm that the two ends can exchange a test message.
- Connect a Nostr client that supports the zap format, such as Amethyst or Primal, to check that messages and zaps appear as expected.
- For payments, configure a Lightning or Cashu wallet, and send a small test amount before relying on it for anything important.
- Keep a written copy of your key backup and the radio settings in a safe place, so you can reconnect if a device fails.
Pros & cons
- Free and open source under the GPL-3.0 license
- Works without a live internet connection on the client side
- Server is designed so it never has access to private keys or user data
- Modular transports let the system work with older and newer radio gear
- Zaps follow NIP-57, so they appear in common Nostr clients
- Mesh routing through Reticulum can keep traffic moving when a link fails
- Code is still being updated, with the latest change dated August 13, 2026
- Windows support is listed in the documentation but has not been independently verified
- Requires radio hardware and some technical knowledge to set up
- Latency is higher than on a standard broadband connection, so real-time chat is limited
- Radio use is subject to local rules, which can restrict encryption on amateur bands
- Requires a separate Cashu or Lightning wallet for payments
Is HAMSTR safe?
HAMSTR involves keys and payments, so take the usual precautions. Download only from the official website or the GitHub repository, and verify the SHA-256 checksum or signature before running the file. Never enter a seed phrase or private key on a third-party website, and be wary of any download link that appears outside the project's own channels.
The project's design keeps private keys on the client side, which reduces the damage a compromised server could cause. Still, a server you run yourself is only as safe as the machine it runs on, so keep the operating system updated and use strong passwords. Because the code was updated recently, the project appears active, but it is not a substitute for reading the repository's latest notes. Check the latest version on the official website before you install.
- Official source only. Download from github.com/LibertyFarmer/hamstr. Ignore ads and lookalike domains.
- Check the SHA-256. Compare the installer hash with the value the developer publishes before running it.
- Never share your seed phrase. No developer, support agent or website — including CryptApps — will ever ask for it.
Alternatives
Most Nostr programs in this catalog, such as Amethyst, Vega, Nostrid, Nostrmo and Notedeck, are clients that connect to relays over the internet. You use them to read and post from a device that has a normal connection. HAMSTR does a different job: it is a bridge that lets a radio-only device reach Nostr at all. It is closer to infrastructure than to an app.
That difference shapes who should choose it. If you have reliable internet, a standard client will be faster, simpler and easier to troubleshoot. HAMSTR is worth considering only when the internet is missing, restricted or unreliable. Among the desktop clients listed, Nostrid mentions Windows binaries directly, which makes it a more predictable choice for everyday Windows use.
Specifications
- Price
- Free
- Type
- Open source
- License
- GPL-3.0
- Latest version
- —
- Last update
- 13 Aug 2026
- Windows support
- Unverified (Windows mentioned in docs)
- Source code
- github.com/LibertyFarmer/hamstr
Frequently asked questions
HAMSTR lets people use Nostr when they have no internet access. A radio-connected server relays requests to Nostr relays, so a client in a remote area or during an outage can still post, read and send zaps. It is mainly used for emergency communication, off-grid work and experiments with radio and mesh networks.
Windows is listed among the supported platforms in the project documentation, along with Linux. Compatibility has not been independently verified, so test the program carefully before relying on it. Check the GitHub repository for current notes on Windows builds and any known issues reported by other users.
HAMSTR is designed so the server does not have access to private keys or user data, which is a strong starting point. Safety still depends on where you download the program and how you run it. Verify the SHA-256 checksum or signature, keep your seed phrase off third-party websites and follow local radio rules.
The client device does not need internet access, because it reaches the network through a radio link. Someone must still run the server on a machine that is connected to the internet and can reach Nostr relays. Without that connected server, the radio side has nothing to relay to.
Yes, the requirements list a Cashu ecash wallet as an option for offline payments that do not need Lightning. Zaps built on Lightning follow NIP-57 and are supported over radio. Choose the payment method that fits your setup, and send a small test payment before relying on either one.
HAMSTR is free and released under the GPL-3.0 license, which means you can use, study, modify and share the code under that license's terms. Because the code is open, anyone can review how it handles keys and messages. Downloads should still come from the official website or the GitHub repository.
Use depends on where you live. Some jurisdictions restrict encryption on amateur radio, and the program's encrypted payment features may fall under those rules. Users are responsible for complying with local regulations, so check your national or regional amateur radio rules before transmitting.
Zaps sent through HAMSTR follow NIP-57, so they appear in clients such as Amethyst and Primal, as well as other Nostr clients that support the standard. The recipient does not need special software to see them. Confirm with the client you use, since display behavior can differ between apps.
Verdict
HAMSTR is a specialized tool for people who need Nostr where the internet is missing or unreliable. It suits ham radio operators, emergency planners, remote-site residents and developers interested in radio transports. It is free, open source and designed so the server never holds private keys. It is not a replacement for a normal Nostr client on a connected device, and Windows use should be tested carefully before you depend on it.