Your balance doesn't exist
A wallet shows you "1.5 BTC" — but there is no balance stored anywhere. Tap the balance and watch what is actually there. Every number you see is computed on the fly from individual coins, each with its own history.
Tap the balance to break it apart
What a coin really is
Each piece is a UTXO — an unspent output from an earlier transaction. Tap one to see what it carries. A UTXO tracks exactly who can spend it next and how much value it holds.
Tap a coin to expand it
Now send 0.8 BTC
Pick the coins to spend. You cannot split a coin — you spend it whole. Tap coins to add them as inputs. The protocol requires every selected UTXO to be consumed entirely; any excess comes back as change.
Goal: send 0.8 BTC
⚠ Not enough — a coin is spent whole, so pick more.
Where change comes from
Your inputs total more than 0.8. The leftover does not vanish — it comes back to you as a second output: change. That change output becomes a brand-new UTXO in your wallet, ready to be spent in a future transaction.
These are the real rules
Every rule here matches the live Bitcoin network — not an approximation, and not an AI guess. Inspect a real transaction yourself. The transaction linked below is the famous 10,000-BTC pizza purchase, the first known commercial Bitcoin transaction.
View a real transaction on mempool.spaceWhere the fee actually is
The fee is not a separate field — it is whatever you leave on the table: inputs minus outputs. Drag the fee rate and watch your change absorb it. Miners rank pending transactions by fee rate (satoshis per virtual byte), so a higher rate means faster confirmation.
- Fee
- 0.00000000 BTC
- Change (back to you)
- 0.00000000 BTC
fee = inputs − recipient − change
Locks and keys
Each output is locked to an address. To spend an input you must prove you can open its lock — by signing. Sign the transaction to make it valid. The signature covers all the transaction data, so no one can alter the outputs after you sign without invalidating it.
Broadcast → mempool → block
Sending does not confirm instantly. Your transaction joins the mempool, sorted by fee rate. Miners take the top of the queue into the next block. Once included, the transaction is irreversible — the UTXO you spent is gone forever and the recipient's new UTXO is created.
Sign the transaction first (previous step).
Compared to asking ChatGPT or reading an article, this whole walkthrough was…
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