Nostr Keyx is a free, open-source browser extension for people who use Nostr and want their private keys kept out of ordinary web pages. It follows NIP-07, a convention that lets websites ask an extension to sign messages without ever seeing the key itself. The project is released under the MIT license and is written mainly in JavaScript and TypeScript.
Read this before you install: the project's last code update was on April 23, 2023, more than two years ago. It may still function for some users, but it has not received code updates since then, so weigh that carefully before trusting it with keys. The latest listed version is v1.5.0. Its best case is a user who wants hardware or OS-level key protection and understands what a signer does.
What Is NIP-07 and How Browser Signing Works
Nostr is a decentralized protocol in which your identity is a key pair rather than a username and password held by a company. Every post, reaction or profile update is an event that must be signed with your private key. Many web clients want to sign on your behalf, which raises an obvious question: where should the key live?
NIP-07 answers that by defining a standard way for a web page to ask a browser extension for a signature. The page sends the unsigned event, the extension handles the request, and the signed result returns to the page. The key itself never has to be pasted into the website, which is the main reason this pattern is popular.
Nostr Keyx sits in that role. It holds the key and produces signatures, so its storage and security model matter far more than the look of any single client. Understanding this split helps you judge whether a signer is worth trusting.
Who Should Consider a Browser Signer Like This
A browser signer is most useful when you use several Nostr web apps and do not want to hand your key to each one. Imagine logging into a microblogging client, a long-form reader and a relay dashboard in the same browser. A single signer lets you approve each action without re-entering key details on every site.
People who use a shared or semi-trusted computer may also value keeping keys out of plain browser storage. Pairing the extension with a YubiKey 5 Series takes this further, since the key lives on a physical token you control. This setup is less convenient for everyday posting, but it keeps the private key off the computer's ordinary storage.
If you only read Nostr occasionally or prefer a full desktop app, you may not need a separate signer at all. Check whether a single client already covers your needs before adding another moving part to your setup.
Key Terms: Private Keys, Public Keys and Recovery
On Nostr, your public key identifies you to others, and your private key proves that you authored an event. Many clients display public keys in encoded forms such as npub, and private keys as nsec. Anyone holding the private key can publish as you, so it deserves the same care as a bank password, with more permanence.
Signing is the act of using the private key to produce a cryptographic proof attached to an event. Other users and relays can check that proof with the public key without learning the secret. This is why a signer never needs to show the key to a website.
Recovery is the hard part. Nostr has no central server that resets your key if you lose it, so a backup or hardware token is essential. Before relying on any signer, decide where your backup lives and confirm that you can restore access.
Key features
Native OS keychain storage
YubiKey OpenPGP support
Small dependency footprint
Supported coins
Bitcoin (BTC) and Nostr are both mentioned in connection with the project. Nostr Keyx is built around Nostr identity keys, and its job is signing Nostr events rather than holding coin balances. It is not a replacement for a Bitcoin wallet.
How to install Nostr Keyx on Windows
- 1
Check Windows compatibility
Windows is among the platforms the project lists, but confirm that a Windows-compatible build is available before you rely on it. Open the Releases page on GitHub and look for files that match your system. Download only from the official website or the project's GitHub Releases page.
- 2
Download the latest release
On the GitHub Releases page, choose the newest version, currently v1.5.0. Avoid mirrors, repackaged copies and download links shared in chats or forums, even if they look official.
- 3
Verify the file
Compare the SHA-256 checksum of the downloaded file with the value published alongside the release. A mismatch means the file should be discarded and downloaded again from the official source.
-
Install in your browser
Follow the installation notes included with the release files or in the project's README for your browser. Once the extension is installed, move on to choosing where your key will be stored.
System requirements
- A Windows PC, provided a Windows build is available on the releases page
- A browser that supports extensions
- A YubiKey 5 Series device, only if you want hardware key storage
How to use Nostr Keyx
Once the extension is installed, setting it up takes only a few minutes. The exact screens depend on the release, so compare them with the instructions included in the project's documentation as you go.
- Open the extension from your browser's toolbar and review the settings page.
- Choose where the key is stored: the OS keychain for everyday use, or a YubiKey 5 Series if you want hardware protection.
- Add your key or connect your YubiKey, following the prompts on screen.
- Open a Nostr web client that supports NIP-07 signing and sign in through the extension.
- Read each signature request carefully and approve only actions you intended.
- When you finish, lock the extension or log out of the client, especially on a shared computer.
Keep a separate, tested backup of your key before step two, because recovery on Nostr is not automated. Then test with a low-stakes action, such as a short test post, to confirm that signing works before you rely on the setup more broadly.
Pros & cons
- Keeps keys in the OS keychain instead of plain browser storage
- Offers YubiKey 5 Series support for hardware-backed keys
- Small dependency list means less third-party code to review
- Free and MIT licensed, with source code on GitHub
- Follows the NIP-07 signing convention
- Last code update was April 23, 2023, with no updates since
- Windows builds should be confirmed on the releases page
- Focused on signing, not a full Nostr client or wallet
- Requires some comfort with key backup and browser setup
Is Nostr Keyx safe?
Nostr Keyx handles private keys, so treat installation as a security decision. Download only from the official website or the project's GitHub Releases page, and verify the SHA-256 checksum before installing. Never type a private key or backup phrase into a third-party website or an unfamiliar form, and be wary of anyone who asks for one.
The project's last code update was on April 23, 2023, and it has not been updated since, so it should be considered unmaintained. Check the latest release yourself on the official website, review the source code on GitHub if you can, and keep a tested backup so that an abandoned tool does not lock you out of your identity.
- Official source only. Download from github.com/susumuota/nostr-keyx. 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 programs in this group are Nostr clients or apps built on the protocol, such as Vega, Nostrid and Notedeck. They give you a full interface for reading, posting and browsing relays. Nostr Keyx is narrower: it sits in your browser and signs events for web apps that request signatures. Bold Bitcoin Wallet and Bro App also build on Nostr, but for wallet pairing and bill payments, so they serve different goals. If you want a full desktop experience, a client is the better fit. If you want a single signer for several web apps, Nostr Keyx is the more relevant tool.
Specifications
- Price
- Free
- Type
- Open source
- License
- MIT
- Latest version
- v1.5.0
- Last update
- 23 Apr 2023
- Windows support
- Likely (builds for Windows; check releases)
- Source code
- github.com/susumuota/nostr-keyx
Frequently asked questions
It can be used with care, but its last code update was on April 23, 2023, so it is not actively maintained. Download only from the official website or GitHub Releases, verify the SHA-256 checksum, and never enter a private key on a third-party site. Keeping a tested backup reduces the risk of losing access if you stop using it.
Windows is among the platforms the project lists, but confirm that a Windows build is available on the releases page before relying on it. Pick the newest release, check that the file matches your system, and verify its checksum. Because it is a browser extension, it runs inside the browser you already use on Windows.
NIP-07 is a Nostr specification that lets web pages request signatures from a browser extension instead of asking for your private key. The page sends an unsigned event, the extension signs it, and the page receives the result. This keeps the key out of individual websites and makes it easier to use one identity across several Nostr apps.
Yes, the project lists YubiKey OpenPGP support for the YubiKey 5 Series. With a hardware key, the private key sits on a physical token rather than in software storage. Set up the token carefully and keep a backup, because losing access to the device can lock you out of your Nostr identity.
Yes, it is free and released under the MIT license, which allows reuse under the license terms. You can find the source code on GitHub. Free software still carries the risks of any key tool, so review the safety guidance before installing.
Bitcoin (BTC) is mentioned in connection with the project, but Nostr Keyx signs Nostr events rather than managing Bitcoin balances. If you need a Bitcoin wallet, use a dedicated wallet program instead. Keeping the two roles separate helps you avoid confusing a Nostr signing key with coin funds.
Verdict
Nostr Keyx suits Nostr users who want a focused tool that keeps private keys out of ordinary browser storage, especially those comfortable with a YubiKey. Its small dependency footprint and MIT license are appealing, but the last code update in April 2023 means it should be treated as a cautious choice rather than a long-term default. If you need ongoing support, consider a more actively maintained signer or client instead.