Header chain
Each 80-byte block header must link to the previous one and meet the proof-of-work target. MultiBit follows the valid chain with the most accumulated work.
How MultiBit Verifies Transactions
MultiBit is an SPV wallet. This page explains what it checks itself, what it takes from peers, and where the limits of that model are.
The verification flow
Simplified Payment Verification (SPV), described in section 8 of the Bitcoin whitepaper, checks transaction inclusion without downloading every block in full. Follow the sequence from receiving headers to counting a payment’s confirmations.
Step 1 of 5Default port 8333
Peers
The wallet opens connections to several Bitcoin peers. They are the source of every header and transaction it receives.
What is checked
- Several independent connections rather than one source
- Requests only the data relevant to the wallet
The limit
A peer can delay or withhold data. Connecting to more than one peer reduces the effect of any single one.
What MultiBit checks itself
Transaction inclusion
For transactions involving your wallet, peers supply a Merkle proof. MultiBit checks that the proof leads to the Merkle root in a header it has already verified.
Confirmation depth
Confirmations are counted from the verified header chain, not taken from a peer's claim.
What it relies on peers for
A verified header chain is not a complete view of everything happening on Bitcoin. These are the boundaries of the information the wallet receives.
Finding transactions
Peers supply transactions matching the wallet’s filter. A peer can omit or delay a match; checking an inclusion proof cannot reveal a transaction the wallet never received.
Block validity
An inclusion proof does not establish that every transaction in a block obeys the consensus rules. SPV relies on the assumption that the chain with the most work is maintained by honest mining power.
Unconfirmed payments
Peers can announce a transaction before it enters a block. Until inclusion is proven, its presence in the wallet is an announcement rather than evidence of confirmation.
SPV compared with a full node
The choice is how much verification to perform locally and how much data to process. Compare the checks, trust assumptions, and resource costs of each method.
Headers, matching transactions and proofs80 bytes per header
Conceptual data illustration, not a storage or performance measurement.
- Data received
- Block headers, wallet-related transactions, and inclusion proofs. Unrelated block contents are not downloaded in full.
- Verification
- Checks header proof of work and transaction inclusion, but does not execute every transaction’s scripts.
- Resource trade-off
- Less data to download and store because the wallet does not process every transaction. Actual usage depends on wallet activity.
- Trust model
- Assumes honest majority mining power and depends on peers to disclose relevant transactions. Inclusion checks do not replace full rule validation.
SPV suits a lightweight desktop wallet; full validation suits users who want to check all consensus rules themselves. Simply running a separate node does not change how MultiBit verifies payments.
Practical guidance
Use transaction details and synchronization status to decide what to check next when a payment arrives, remains pending, or appears to be missing.
Check 01
Check the payment’s confirmation count
- When to check
- Before handing over goods or marking an invoice paid.
- What to do
- Open the incoming payment in Activity. Check its amount and confirmation count against the payment terms you agreed with the sender.
- Keep in mind
- Do not rely on a sender’s screenshot. There is no confirmation count that guarantees a payment cannot be reversed.
Check 02
Read the status of the specific transaction
- When to check
- A payment appears in Activity but you are unsure whether it has completed.
- What to do
- Open its details and check whether it is pending or confirmed. If you are comparing records with the sender, compare the transaction ID, not just the amount.
- Keep in mind
- A synchronized wallet can still show a pending payment. Sending again creates a separate payment; it does not confirm the first one.
Check 03
Check synchronization before trusting a balance
- When to check
- Recent activity is missing or the displayed balance seems out of date.
- What to do
- Check the connection and synchronization status. Keep the wallet online while it catches up, then reopen the transaction details. If data is still missing, follow the troubleshooting guide.
- Keep in mind
- Saved wallet data can be incomplete while synchronization is unfinished. Do not delete wallet files or restore the wallet just to refresh the display.
See how peers keep the wallet current
Explore connections, synchronization, and what network status tells you.