Olesia.

A Bitcoin wallet built from scratch on audited primitives — cold generation, honest entropy, and a testnet playground you can actually use.

For Olesia — my beautiful one. The name, and everything good here, is for you. ♥

Learn Bitcoin, safely. Olesia is an educational wallet — practise with real keys, real transactions and every script type on test networks where mistakes cost nothing. We believe it's the first to bring a faucet and every Bitcoin script type together in one open, verifiable place. Please don't keep meaningful amounts of Bitcoin here — it's a learning tool, not a bank. Read the manifesto →

1 · Cold generator →

Start here. Create a 24-word seed, backup and watch-only descriptor. Built to run offline.

offline.olesia.io

2 · Open the wallet →

Then use it: send, receive, sweep and message. Balances, QR, history. Runs in your browser.

app.olesia.io

The one rule. For any wallet you will fund with real value: download the cold generator, verify its hash (below), disconnect from the internet, and run it offline. A page served over the web can be changed by whoever controls the server — verifying the hash and running offline removes that trust. The online wallet is for testnet and small amounts.

Verify the cold generator

The build is byte-reproducible. Confirm any copy you download is exactly the reviewed code:

curl -sL https://offline.olesia.io -o olesia.html
sha256sum olesia.html
# expected:
8873a809524ba65a424902c0b592bd15a7888b3e587244ee04b1ce5caf963ef2

Full instructions and an independent Sparrow round-trip are in VERIFY.md. Source, security audit and reproducible build: github.com/testnetbtc/BTC_Wallet.

How it's built

Cold generator — audited @scure/@noble primitives, 256-bit entropy from the OS CSPRNG, fail-closed self-check, encrypted authenticated backups, reproducible single-file build.
Online wallet — signs locally with @scure/btc-signer (RFC-6979); balances/broadcast over the network; never stores your seed.
Mainnet (coming) — air-gap only: watch-only online, sign offline, broadcast through your own node. The seed never goes online.

Olesia is experimental and self-audited. Not financial advice; not a substitute for a hardware wallet for large sums. Testnet first, always.