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slide 13 · fundamentals

BTC & ETH transfers

you
mempool
block
them

Send simulated coins: BTC spends on .space, ETH updates an account on Etherscan.

  1. 1Pick BTC or ETH and set a fee
  2. 2Send and follow each stage
  3. 3Watch confirmations pile up
live · 0 players in this room

send coins to another player

10.0000 BTC10.0000 ETH
recipient

waiting for another player to join this room… open this page in a second tab or share the link with the class.

fee 0.0005 · total 0.5005 BTC
live transfers in this room
room ledger · tap a row to replay its steps
  • no transfers yet — be the first to pay a classmate.
UTXO transfer · mempool.spaceidle
sender · you
yyour wallet
spends UTXOs
bc1qaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
1.4000 BTC
mempool
block
confs
0.05
receiver
rrecipient
gets a new UTXO
bc1qbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
0.0000 BTC
you send
0.05 BTC
network fee
6,732 sats
wait for inclusion
1 block(s) · 12 min
6 confs in
72 min

Your wallet

≈ $3,200 USD · + fee 6,732 sats
Speed
network fee · sat/vB market
miner priority queue
tx size374 vB (2 in / 2 out)
fee rate18 sat/vB
total fee6,732 sats
in BTC0.00006732 BTC · $4.31
queue rank#497
est. inclusion~1 block(s)

What happens in the background

Drag the amount, fee and congestion sliders — the fee, ETA, queue position and the travelling coin all react instantly, even mid-flight. Each stage stage opens an explainer — click any completed stage to read it again.

confirmation blocks0 / 6
1
2
3
4
5
6
statusunconfirmed · reversible
reversal odds100%
block time~10 min

Each block buried on top forces an attacker to redo that proof of work and outpace the honest chain. Six deep is the merchant standard.

fee & gas breakdown · per stepsat/vB
build · fee is bid per byte
tx size374 vB (2 in / 2 out)
fee rate18 sat/vB
fee = size × rate6,732 sats
in fiat0.00006732 BTC · $4.31
sign · fee is locked into the signature
inputs spent0.30006732 BTC
to recipient0.05 BTC
change back0.25 BTC
implicit feeinputs − outputs = 6,732 sats
mempool · your bid vs everyone else's
your bid18 sat/vB
queue rank#497
est. inclusionnext block · 12 min
bumpableyes — replace-by-fee (BIP-125)
block · who gets paid
miner fee6,732 sats
block subsidy3.125 BTC (newly minted)
burned0 — Bitcoin burns nothing
refundnone — the whole bid is spent
confirm · final cost
sent0.05 BTC
fee paid0.00006732 BTC · $4.31
total debited0.05006732 BTC
to full settlement72 min
live mempool · reordered by fee every block8 pending · block #869,412
next block cut-off
#1bc1q601c…567f27 sat/vB
#2bc1qae8d…ae1825 sat/vB
#3bc1q00fb…867323 sat/vB
#4bc1qfd9f…f8d022 sat/vB
#5bc1q5522…e53a17 sat/vB
#6bc1q42c8…354816 sat/vB
#7bc1q89af…9ed013 sat/vB
#8bc1q3e32…248c10 sat/vB
your rank
est. inclusionnot in the mempool · 0 s
6 confs in60 min
  • watching the queue… bids move every couple of seconds.

Nothing is queued in order of arrival: miners sort by sat/vB, so a later, richer transaction overtakes yours. Replace-by-fee re-signs the same inputs with a higher fee — nodes forget the old version, and only one of the two can ever confirm.

distributed ledger & immutabilityidle
network············

Every node holds a full copy of the ledger. Broadcast a transfer to watch it spread.

hash-linked chain

Tap any block to edit it. Each block stores the previous block's hash, so a single change cascades.