Olesia Wallet.
Online send / receive across every script type — testnet. New to Bitcoin? Learn the basics →
Hot wallet. Your seed is typed into this page and used to sign in your browser. It is
never stored and never leaves this tab, but a web page is not cold storage. Fine for testnet, and
for small mainnet amounts you'd accept losing (like any mobile wallet). For meaningful funds, load a
watch-only xpub here and sign offline — never put a large-balance seed in a web page.
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New here? Four steps 👋
- Pick a network — Signet is smoothest (regular blocks, free coins).
- Tap Generate new, then Load. Write the 24 words on paper.
- Receive: copy your address, get free coins from a faucet.
- Send anywhere, add an OP_RETURN message, or switch script types to explore.
All testnet-safe. Learn the concepts →
Bitcoin has several chains that share the same rules. Testnet3/4 and Signet use free, worthless coins for practice (Signet has regular ~10-min blocks — the nicest to learn on). Mainnet is real money.
Your wallet is these 24 words (the BIP-39 standard). Anyone with them controls the coins — there's no "reset". Write them on paper, in order; never screenshot or cloud-sync them. An xpub is a public key that can watch a balance but cannot spend.
A transaction spends your UTXOs (coins) as inputs and creates outputs: one to the recipient, and usually one back to you as change. You choose the destination address and amount (in sats).
Write a message on-chain. OP_RETURN attaches a tiny permanent note (~80 bytes) to a transaction. It carries no coins and can never be spent — just a line written into Bitcoin's public record, forever. Real uses: proving a document existed at a point in time, notarising, attribution, a personal message or memorial. The famous one: Satoshi wrote a newspaper headline — "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks" — into the very first block (in the coinbase field; OP_RETURN is today's tidy way to do the same). Where we stand: people disagree about what data belongs on Bitcoin, and Olesia takes no side — it's part of the protocol, so it's here, explained, for you to use thoughtfully.
Miners include transactions that pay them, priced in satoshis per virtual byte (sat/vB). Higher = confirms faster. On testnets fees barely matter, so it is a safe place to experiment.
A sweep empties the whole wallet to one address in a single transaction — no change output. Handy for moving everything to a new wallet.
Balances/broadcast via mempool.space. No analytics, no storage. Source: the packages/bitcoin module, signing with @scure/btc-signer.